A rebel unit of army defectors launched a major offensive against security facilities in Syria's largest city of Aleppo, and anti-regime forces targeted air bases to try to reduce the military threat from the skies, activists said Friday.

The coordinated attacks by the Brigade of Free Syrians pointed to a higher-than-usual degree of planning by the rebels, suggesting that President Bashar Assad's opponents are becoming more brazen as the civil war deepens.

The Local Coordination Committees, an activist group that monitors violence and rights abuses in Syria, said rebels shot down a helicopter in the town of Sarmeen, in the northeastern province of Idlib. An activist in the area also reported a helicopter was downed.

The reports could not be independently verified, but if confirmed, it would be the second such aircraft to be downed by rebels this week. One helicopter was downed in Damascus on Monday.

Nearly 18 months into the uprising against Assad that has become a civil war with more than 20,000 people estimated to have been killed, the International Red Cross painted a grim picture of life in Syria. It said the humanitarian needs of civilians were rising and medical care was becoming more and more scarce.

"People fear for their lives every minute of the day," said Marianne Gasser, the head of the ICRC delegation in Syria, in a report released in Geneva.

"Every day, dozens of people are killed in the fighting, and increasing numbers of people succumb to their wounds, unable to obtain medical care because of the fighting and the lack of medical supplies, or simply because medical care is not available in their areas," she said.

The three coordinated attacks in the northern city of Aleppo began before midnight Thursday and ended Friday morning — two days after Assad conceded that his forces have been unable to quell the rebellion.

Weeks of intense bombardment by the Syrian military, including airstrikes and artillery shelling, have failed to dislodge the rebels. Instead, it seems to have emboldened them.

Assad's military, the backbone of his 12-year rule, is bogged down in a stalemate for control of Aleppo and unable to crush the rebels in the capital of Damascus and its suburbs. It also is fighting smaller-scale battles in the south and east.

Dubbed "Northern Volcano," the rebel offensive in Aleppo targeted an artillery training school, a compound of the feared air force intelligence, and a large army checkpoint, according to Mohammed Saeed, an activist based in the city, which is Syria's commercial capital. The offensive will focus on specific military and intelligence targets in Aleppo and the surrounding province of the same name, he added.

The three simultaneous attacks left an unspecified number of troops dead or wounded and badly damaged the top floor of the main, two-story building in the air force intelligence compound, Saeed said via Skype.

Rami Abdul-Rahman, director of the Britain-based Syrian Observatory for Human Rights, also said rebels killed and wounded regime forces at an air force compound in Aleppo's Zahraa neighborhood, but had no details on the other two attacks reported by Saeed.

Rebels seized several areas in Aleppo last month, signaling a turning point in the conflict because the region had long been spared major violence. Rebels also control much of the wider Aleppo province, including areas on the border with Turkey.

Rebels in northern Syria said they are fighting for control of an air base in Idlib province, the second such facility to come under attack this week. Activists say a third air base, also in the north, came under attack Friday, with rebels hitting it with mortar rounds, antiaircraft guns and rocket-propelled grenades.

Activists say the attacks on air bases are in response to the growing use of aircraft by the regime, possibly to bolster its firepower as troops are stretched thin due to fighting on a multitude of fronts. The rebels have no effective weapons against the regime's fighter jets and helicopter gunships, except for antiaircraft guns that they mostly use against ground troops.

"The regime's air power is severely restricting the movement of the rebels on the ground," said Saeed, the Aleppo-based activist. "We need anti-aircraft missiles, but we may never get them."

In an interview with a privately owned Syrian TV channel shown Wednesday, Assad said his military needed time to win the war, but claimed the conflict has drawn regional and international powers to the side of the rebels. Syrian authorities often cite Turkey, Saudi Arabia and Qatar as the rebels' main backers.

Fighting continued elsewhere in Syria on Friday, including Damascus, where intense battles have been raging for more than a month. The Observatory and the Local Coordination Committees also reported clashes and shelling between troops and rebels in the southern province of Daraa and the central region of Homs.

By late Friday, the observatory said as many as 100 people were killed across Syria.

Heavy clashes continued for a third day around the sprawling Abu Zuhour air base in Idlib province, the Observatory said. Fadi Al-Yassin, an Idlib-based activist, said there were unconfirmed reports that three fighter jets were damaged by rebel shelling.

Al-Yassin said the attacks on Abu Zohour and the Taftanaz air base Wednesday were designed to curtail the regime's air power. He said 10 military helicopters were badly damaged in Taftanaz. Grainy photos of damaged helicopters purportedly in Taftanaz were posted on the Internet this week. The authenticity of the images could not be independently verified.

"The objective of the attack on Abu Zohour is to damage the runway as well as the jet fighters," Al-Yassin said by satellite phone from Idlib.

Rebels said they shot down a fighter jet Wednesday in Idlib, and Al-Yassin said it was hit by gunfire shortly after it took off from Abu Zohour. The two pilots bailed out; one was captured and the second was killed by rebels when he tried to resist, he added.

Video posted online by the rebels showed a body in olive-drab pilot's fatigues with what appeared to be a head wound. A white parachute lay nearby.

The video could not be authenticated.

Saeed said another Aleppo-area airport, Quiras, came under attack Friday.

In Paris, French Foreign Minister Laurent Fabius warned that France would respond with military force if Assad uses his chemical weapons.

"Our response would be immediate and sharp as lightning," Fabius said Friday on Europe-1 radio, suggesting that France would not wait for U.N. permission.

"Bacteriological and chemical weapons are of a different nature from ordinary arms," he said. "We cannot tolerate that these weapons, whose fallout could spread, would be used."

Syria said in July that it could use chemical or biological weapons if it were attacked from outside.

Syria is believed to have nerve agents as well as mustard gas, Scud missiles capable of delivering these lethal chemicals and a variety of advanced conventional arms, including anti-tank rockets and late-model portable anti-aircraft missiles.

The U.N. refugee agency reported a growing number of Syrians fleeing to Lebanon's eastern Bekaa Valley, near the Syrian border, with about 2,200 arriving in the past week. That's almost double the weekly average, agency spokesman Adrian Edwards said.

Another 400 Syrians are reaching northern Lebanon each week, he said in Geneva.

Edwards said Turkey has opened two more refugee camps for Syrians in the past week and is now hosting 80,410 people in 11 camps and schools in its border provinces.

Also in Geneva, former U.N. Secretary-General Kofi Annan quietly ended his stint as a would-be peacemaker for Syria on Friday, with the task now being taken up by another veteran U.N. diplomat, Lakhdar Brahimi.

Unlike Annan, who was based in Geneva for six months, Brahimi will make his center of operations in New York, where he hopes he can better influence the U.N. Security Council to unite around a plan to end the violence.

Annan blamed divisions on the 15-nation Security Council for the failure to persuade Assad and the opposition to end the conflict.

Russia and China used their vetoes on the council to block U.N. sanctions against the Syrian regime, despite entreaties by the U.S. and other Western nations.

Brahimi, a former Algerian foreign minister who has been a U.N. envoy to Afghanistan and Iraq, said his first task will be to overcome the divisions in the Security Council and get it to speak "with a unified voice."


Associated Press writer Angela Charlton in Paris and Frank Jordans in Berlin contributed to this report.