A female suicide bomber set off a powerful homemade explosive device outside a Moscow subway station Tuesday, shooting shrapnel through a crowd of commuters and killing at least 10 people and injuring 51, authorities said.

The explosion transformed a mild late-summer evening in northern Moscow into a bloody scene of screaming bystanders, burning cars and rescue squads. Some bodies were found dozens of yards from the explosion, authorities said.

The bombing occurred exactly a week after explosives downed two Russian passenger jets almost simultaneously, killing 90 people in one of the deadliest attacks on civilian targets in Russia in years. Russian authorities have been investigating two female passengers with Chechen surnames who boarded the planes on last-minute tickets.

An Islamic extremist group with apparent ties to al Qaeda that claimed responsibility for the plane crashes asserted that it carried out the Tuesday night bombing, as well. "We in the Islambouli Brigades announce our responsibility for this operation . . . which comes in support of Muslims of Chechnya," it said in a statement, according to news agency reports from the Middle East.

Even before the subway station bombing, Russian news media reported that two other Chechen women accompanied the suspected plane bombers to Moscow in the days before the crashes and were still at large in the capital. Anticipating further attacks, authorities had stepped up security across the city, and initial reports Tuesday night suggested that the suicide bomber turned away from the subway station after seeing police officers checking documents at the entrance.

"She got scared of them, turned around and decided to blow herself up among the people," Moscow Mayor Yuri Luzhkov told reporters after rushing to the scene. "There were many people there. The explosion was very powerful."

The Moscow subway system was bustling Tuesday with returning vacationers on the last day of summer vacation before the opening of schools. The Rizhskaya station is situated just off Prospekt Mira, or Boulevard of Peace, one of the city's major thoroughfares.

The bomb contained about two pounds of TNT along with iron bolts and metal fragments, officials said. The explosion, at about 8:15 p.m., set two cars on fire and pelted passersby with metal shards. The blazing automobiles sent plumes of dark smoke into the air. At first, witnesses thought a car bomb had exploded, but then it became clear that a woman had blown herself up.

Images broadcast on Russian television showed residents staggering in apparent shock, some with their faces or clothes covered in blood. Nearby shop windows were shattered. Rescue workers loaded bodies onto blue tarps and hauled them away. Seven people, including the bomber, were killed instantly, and others later died of injuries, officials said. Three children were reported among the wounded.

Another bomb loaded with metal fragments injured four people at a bus stop on the road to Moscow's Domodedovo Airport last week shortly before the doomed planes took off. It was unclear whether that blast was related to the later attacks.

The Tuesday bombing was the second to target the Moscow subway in six months. In February, a blast inside a subway car killed more than 40 people. Altogether, more than 600 people have died in terrorist attacks in Russia in the past two years. Most of the attacks have been related to the war in the separatist republic of Chechnya, where Russian troops are battling guerrillas fighting for independence.

The subway attack Tuesday came hours after President Vladimir Putin made his first public comments about the plane crashes since authorities said that they were the result of terrorism.

At a televised news conference in the resort city of Sochi alongside visiting French President Jacques Chirac and German Chancellor Gerhard Schroeder, Putin tied the attacks to al Qaeda, relying on an Internet claim made by a group calling itself the Islambouli Brigades.

While noting that the claim had not yet been authenticated, Putin said it proved his long-standing argument that Chechen rebels have been aided by international terrorist organizations. "If one of the terrorist organizations has assumed responsibility for this and it is linked to al Qaeda, that is a fact that confirms the link between certain forces operating on the territory of Chechnya and international terrorism."

Putin also defended the legitimacy of Sunday's election for president of Chechnya, a vote widely criticized by human rights groups and U.S. and European officials as having been manipulated to install a Kremlin ally, Alu Alkhanov.

"It is impossible to drag people out of their homes by the scruffs of their necks or by their hair," Putin said, scoffing at allegations of fraud and ballot-box stuffing. "If a person doesn't want to go to the polls, he won't. This is called voting with one's feet."

Firefighters douse two cars set ablaze when a woman set off a powerful home-made bomb outside a subway station crowded with returning vacationers.Rescue workers give first aid to one of those injured in the attack at a station in northern Moscow.