Israeli forces fired a missile and a barrage of tank shells to hold back a crowd of Palestinians protesting military operations in Gaza (search) on Wednesday, killing at least 10, including children and teens. Overwhelmed doctors treated some of the dozens of wounded on blood-drenched hospital floors.

Five more Palestinians were killed in separate incidents early Thursday.

White smoke rose into the air as Palestinians carried the wounded — including children with bloodied faces — from the scene. Some were evacuated to the hospital in donkey carts, witnesses said.

"I could see the tank, first it fired a tank shell, it landed next to an electricity pole," said Hisham Ashour, 45, who was near the front of the crowd. "We immediately started picking up the wounded who had collapsed to the ground. Many of them were kids."

The strike, captured in dramatic television footage, provoked unusual criticism from the Bush administration, anger throughout the Arab world and condemnation from European leaders. British Prime Minister Tony Blair (search) called Israel's 2-day-old military offensive in the Rafah (search) refugee camp "unacceptable and wrong."

The U.N. Security Council (search) called on Israel to halt the demolition of Palestinian homes and condemned the killing of Palestinian civilians. The United States, which could have vetoed the resolution, abstained in the 14-0 vote.

In two incidents early Thursday, five more Palestinians were killed. Three militants were killed in a missile strike in the Rafah camp near the Egyptian border around midnight, doctors said. The military said a helicopter fired at gunmen approaching Israeli forces. Before daybreak, two militants were killed by a tank shell near the border, doctors said.

In a statement, the Bush administration said it deeply regretted "the loss of life of innocent Palestinian civilians today in Gaza," and said the deaths "serve as a grim reminder of the wisdom" of Israel's pulling out of Gaza.

Secretary of State Colin Powell also criticized Israel, saying "the activities of the Israeli defense forces in Gaza in recent days have caused a problem and have worsened the situation."

Israel expressed regret over the deaths and said the casualties were a result of warning shots to hold back the crowd after several gunmen were spotted among several thousand marchers.

But Defense Minister Shaul Mofaz said the growing international condemnation would not deter Israel from pressing ahead with its offensive in the camp to hunt down militants and destroy arms-smuggling tunnels.

Late Wednesday, three Palestinian militants were killed in a missile strike in the Rafah camp, doctors said. The military said a helicopter fired at gunmen approaching Israeli forces.

Residents earlier reported that Israeli infantry and tanks moved into an area of the camp next to Rafah town and traded gunfire with Palestinian gunmen.

Early Thursday, Israeli forces destroyed a four-story building in the camp belonging to Islamic Jihad leader Nafez Azzam and a small Islamic sports club, residents said.

Thirty-seven Palestinians have now been killed since Israeli forces invaded the camp's Tel Sultan neighborhood early Tuesday. Palestinians said most of the casualties in "Operation Rainbow" were civilians.

The massive invasion — the largest in the Gaza Strip in years — came less than a week after Palestinian militants killed 13 soldiers in Gaza.

The fighting has revived debate inside Israel on its continued presence in Gaza. Israeli Prime Minister Ariel Sharon has proposed withdrawing from the volatile area, but his Likud Party rejected the proposal this month. Sharon has pledged to push forward with his plan.

The tank shelling came Wednesday afternoon as Palestinians marched from the town of Rafah to the nearby refugee camp to protest the Israeli invasion. An Israeli helicopter flew overhead, firing several flares toward the marchers as machine gun fire was heard. Moments after the flares descended, a large explosion went off in the crowd. Witnesses said a tank shell caused the blast.

Associated Press Television News footage showed smoke and debris flying, followed by Palestinians carrying away the wounded, including several children with bloodstained faces.

The army said Israeli soldiers fired about four tank shells at an abandoned building, which blocked their view of protesters who were passing on the other side at that very moment. At least one of the shells tore through the building and hit the crowd. Israeli forces also fired a missile and machine guns but said nobody was hurt as a result.

Israeli army chief Lt. Gen. Moshe Yaalon said troops did not deliberately fire on marchers.

"No commander or soldier gave an order or got an order or deliberately aimed at civilians ,and we're sorry that innocent civilians got hit. We don't aim at Palestinian civilians," Yaalon said.

Palestinian leader Yasser Arafat called the strike "genocide" and a "massacre that stands against all humane, civilized and political principles." Thousands of Palestinians, many waving green flags of the militant movement Hamas, marched in Gaza City on Wednesday evening to condemn the Israeli attack. About 1,000 people marched in the West Bank city of Ramallah.

Dr. Moawiya Hassanain, a Palestinian Health Ministry official, said at least 10 people were killed and 50 wounded, 36 of them critically. Among six of the dead identified by Wednesday evening, four were children, ranging in age from 9 to 14. The two others were 17 and 20. Most of the wounded were youngsters.

The stairs and floors at the Rafah hospital were drenched in blood as doctors shouted for help and blood donations. Hospital staff treated the wounded on the floors after quickly running out of beds.

"Until this moment I can't imagine how we dealt with the cases — burn cases, cases of people whose insides were exposed, kids screaming and blood everywhere," said hospital director Dr. Ali Mousa.

"I have been working here since the beginning of the intifada, we have faced many similar situations, but, today was the worst I've ever seen," he added.

With the small hospital morgue overflowing, bodies were stored in a refrigerated vegetable storeroom nearby. Dozens of Palestinians lined up at the hospital to give blood.

"The least we can give is our blood, we have nothing to offer," said Sami Abu Irmana, 19, his blue shirt stained with blood from a shrapnel wound in his shoulder.

Residents of the refugee camp's Tel Sultan neighborhood remained holed up in their homes Wednesday as gunfire crackled in the air.

One of them, Izzidine Adwan, said the Israeli army called on all men to leave their houses so that troops could question them. Adwan said some 3,000 answered the call and that after questioning, 50 were arrested.

Early Wednesday, the army said it demolished the Rafah home of an Islamic Jihad militant it said was responsible for a shooting attack that killed a pregnant Israeli settler and her four daughters this month. Palestinian witnesses said at least three homes were demolished overnight.