Two bombs ruptured busy districts of Turkey's biggest city Thursday, killing at least 26 people - including Britain's most senior official here - and wounding about 450. The nearly simultaneous attacks targeted symbols of the United Kingdom, the country that President Bush only a day earlier called America's best friend in the war on terror.
The British Consulate General and the 12-story headquarters of the British HSBC Bank, situated in crowded business districts, exploded just after 11 a.m., marking the second time in a week that terrorism has spilled onto Turkish soil, despite efforts of the country's leaders to distance themselves from US-led policy in the region.
As families grieve for loved ones, analysts are trying to grasp what the perpetrators are striving to achieve.
"For Al Qaeda, we can understand why Turkey makes sense. It is the only well-functioning country in the Muslim world, and the Islamists who lead the government are trying to take Turkey into the European Union," says Soli Ozel, a political scientist at Istanbul Bilgi University. "The extremists want to make sure that this experiment doesn't succeed."
After the weekend synagogue bombings, authorities tightened security at Jewish establishments and for other religious minority groups such as Greek and Armenian Christians.
But Thursday's bombings fired what some feared is a first shot at political and economic targets, causing panic and a skid in the Istanbul stock market.
In response, Turkish officials can be expected to launch a crackdown on fringe groups with connections to extreme Islamic groups that may have been overlooked in the past. Virtually all acts of terrorism Turkey has experienced over the past few decades has linked to Kurdish separatist groups - not Muslim fundamentalists.
"These are serious attacks in a very short period of time, which will prompt a very authoritarian response," Ozel says. "There are people who will argue that we've given too many groups too much freedom. Why were they not crushed before? Are we talking about a serious intelligence gap here?"
Though Thursday's attacks fit into this week's pattern of sophisticated strikes against Turkey, Britain also felt their impact. The attacks killed British Consul-General Roger Short as well as at least three other British nationals.
More than 20 Turks were also killed, and the numbers were expected to rise. The powerful blasts caused scenes of mayhem that were a macabre rerun of the carnage five days earlier, when two synagogues here were bombed in attacks linked to Osama bin Laden's Al Qaeda organization.
Yet another day of horror, coming near the end of the Islamic holy month of Ramadan - a time when Turks gather with family for joyous celebrations - struck chords of fear, anger, and utter bewilderment among Turks who tend to see themselves as a nation on the neutral sidelines of the global terror war.
"I was just doing my work when I saw a huge truck come at the building," said a dazed man with a bloodied forehead, his black hair full of pulverized glass. "I saw fire and then I found myself on the ground," said the man, a construction worker who held aloft his bandaged arm, tended by medics on the scene minutes earlier, before he wandered away past shattered shops and signs that read "Kutlu Olsun" - happy holiday.
Nevin Ertosun, a young Turkish woman with tears brimming in her eyes, stood outside a overwhelmed city hospital nearby, waiting to donate blood. "Our celebration days are coming now - what kind of Muslim would do this during Ramadan?" she asked. "This is the business of fundamentalists. If they have a problem with Britain, let them complain about it there. Why hit us?"
Turkey has hardly been the most willing participant in the US-led drive for regime change throughout the Middle East and Central Asia.
After the Sept. 11 attacks on New York and Washington, Turkey supported the war in Afghanistan and did a stint last year leading a 4,500-member peacekeeping force in Kabul.
But Turkey was overwhelmingly opposed to the war in Iraq, and in March its parliament voted against sending allowing US troops to enter Turkey to invade Saddam Hussein's territory from the north.
Under strong pressure from Washington, Turkish Prime Minister Tayyip Recep Erdogan convinced parliament in September to send Turkish troops to help coalition forces struggling to maintain security in Iraq. But vehement opposition in Iraq to receiving Turkish troops has forced the Bush administration to backpedal on the offer. Turkey announced earlier this month that it will definitely not be sending troops after all.
Although there are tensions with the United States, Turkey remains keenly pro-Western, and its most powerful state institutions, staunchly secular. That, say international terrorism experts, is enough to move Turkey to the top of any extremist's target list.
"After the first attacks at the synagogue, you could believe it was a local act, or possibly even the Iranians or Turkish Hizbullah, taking responsibility," says Shmuel Bar, a specialist in Islamic radicalism and terrorism at the Institute of Policy and Strategy, Herzilya, Israel.
"But the modus operandi of such a large number of explosions and such of sophistication looks to me more in the line of Al Qaeda. In the eyes of Al Qaeda, it isn't a Muslim country, it's a country taken over by something worse than infidels. Infidels are born infidels, they can't help it. But you can't convert from Islam into another religion, that is apostate. In their eyes, Turkey is in a state of being apostate" - a far graver offense.
Most disturbing for many Turks here was the sense that massive, random violence - something they had been largely spared until now - had arrived in the very heart of downtown Istanbul.
Near the bombed British Consulate Gereral, an old man grasped a wall, squatted low on the pavement and began to wail. "My daughter! My daughter and her husband worked in the consulate," he sobbed. In his hand he clutched a key chain. On it is the crescent and star of Turkey's flag.
• Staff writers Nicole Gaouette and Peter Ford contributed to this story.