Suspected Al Qaeda (search ) homicide bombers blew up trucks packed with explosives at the British consulate and a London-based bank Thursday, killing at least 27 people and wounding nearly 450. The twin attacks coincided with President Bush's state visit to Britain.

The blasts, just minutes apart, were the worst terrorist bombings in this Muslim nation's history, and marked the second attacks in Turkey to be blamed on Al Qaeda this week. On Saturday, bombers struck two Istanbul (search) synagogues, killing 23 people.

Turkey's security forces were put on highest alert, and the army briefly deployed soldiers in the streets. Arab and other world leaders were swift to condemn the bombings in Turkey, NATO's only Muslim member and a close ally of the United States and Israel.

British Consul-General Roger Short (search) and his personal assistant, Lisa Hallworth, were among the dead.

British Foreign Minister Jack Straw, who rushed to Istanbul, said he was aware of 13 deaths at the consulate, including one other Briton. Istanbul Gov. Muammer Guler put the total at 16.

"Once again we are reminded of the evil these terrorists pose to people everywhere and to our way of life," Prime Minister Tony Blair (search) said in London, with President Bush by his side. "There must be no holding back, no compromise, no hesitation in confronting this menace."

Bush said the bombing showed "utter contempt for innocent life."

"The terrorists hope to intimidate, they hope to demoralize. They are not going to succeed," the president said.

U.S. and Turkish officials said the bombings bore the marks of an Al Qaeda operation, with near-simultaneous timing and the use of fertilizer-based explosives.

The first pickup truck exploded outside the Turkish headquarters of HSBC (search), the world's second-largest bank, shearing off the white facade of the 18-story building and exposing the gray concrete beneath. Windows were blown out and scraps of white ceiling material dangled, caught on torn electrical wires swaying in the breeze.

About 10 minutes later, a second truck crashed through the gate of the British consulate five miles away in Beyoglu, a historic district popular with tourists. The vehicle looked like a food delivery truck with the explosives in large metal food containers, the Anatolia news agency reported.

The blast destroyed annexes to the main building and tore apart a wall surrounding the consulate's garden. Wounded people covered in dust and blood staggered away from the area. Two women stood outside the consulate crying and shouting for their relatives.

Shattered glass littered the area.

"Cars were flying, there was blood everywhere," said Mehmet Dag, a delivery man who was just 100 yards from the consulate.

The earlier explosion outside the bank was so strong it scattered body parts and bloodied pieces of charred metal across a four-line highway in front of the building and into a cemetery. A policeman went into the cemetery to collect body parts, including a charred, severed leg that he put inside a plastic bag.

Burned out cars, some with their doors blown open, sat in front of the bank building, located in the affluent Istanbul district of Levent. Some police wore surgical masks against the smoke and stench of burning wires.

An unidentified caller to Anatolia said Al Qaeda and a small military Turkish group, the Islamic Great Eastern Raiders' Front, known as IBDA-C, jointly claimed responsibility for attacks.

Premier Recep Tayyip Erdogan, whose Islamic-rooted political party draws support from some Turks who oppose Turkey's close ties with the West, vowed to defeat the attackers, who struck during the Islamic holy month of Ramadan.

"Those who bloodied this holy day and massacred innocent people will account for it in both worlds," he said. "They will be damned until eternity."

Speaking to Blair, Erdogan also pledged to step up the fight against terror. "There is no faltering," Erdogan said, according to Anatolia. "We shall continue our fight against terrorism with more fervor."

Interior Minister Abdulkadir Aksu said at least 27 people were killed and 450 injured, adding the attacks were carried out by homicide bombers and were similar to the synagogue bombings, in which hundreds of pounds of fertilizer-based explosives were packed into trucks.

In Washington, Attorney General John Ashcroft said the attacks bore the marks of an Al Qaeda operation. "They appear to be in the method of operation, or in the operational style, of Al Qaeda or Al Qaeda operatives or affiliates."

The U.N. Security Council unanimously passed a resolution urging all states to cooperate to track down the perpetrators.

"Those who carried out these attacks have no respect for human life," U.N. Secretary-General Kofi Annan said.

Almost 100 Turkish troops were deployed after the blast. At least a dozen, wearing helmets and camouflage uniforms and armed with G-3 assault rifles, stood by their jeeps near the HSBC headquarters. The troops later withdrew.

Such a deployment is sensitive in Turkey, where the military took power three times between 1960-80. The last coup came after years of street clashes between left wing and right-wing fighters left some 5,000 dead. The coup came at the height of the violence when some 20 people were being killed every day.

It was the highest single-day death toll from terrorism in Turkey since 1977, when gunmen opened fire on leftists celebrating May Day, killing 37.

Turkey's stock market started falling after the attacks and was closed minutes later after plummeting 7 percent. It will remain closed Friday. The central bank said it would act to prevent any fallout from the attack.

Turkey has been recovering from its worst recession in decades and there were fears that the attacks could cut into tourism and scare away foreign investors.

Several countries, including Britain, warned citizens to stay away from Turkey, and Europe's soccer authorities postponed international games in the country. Some Israeli tourists declined to board a plane destined for Turkish vacations.

The U.S. consulate remained open, but Australia closed its offices in the city.

The two homicide bombers who attacked the synagogues on Saturday were identified as Turks who the foreign minister said had visited Afghanistan. Al Qaeda and the Turkish IBDA-C also claimed responsibility for that blast.