MOSCOW - President Vladimir Putin led a national day of mourning Monday and pledged Russia would not surrender to terrorist "blackmail." Relatives and friends grieved for 118 captives who died in the siege at a Moscow theater, all but two from the paralyzing gas used to rescue them.

Using words remarkably similar to those of President Bush after the Sept. 11 attacks in the United States, Putin pledged in televised comments to give the military broader powers to move against suspected terrorists and their sponsors.

"Russia will answer with measures adequate to the threat to the Russian Federation in all places where the terrorists, the organizers of these crimes or their ideological or financial sponsors are located," Putin said. "I emphasize - wherever they may be."

Putin has said the theater raid was planned abroad, and the Russian Foreign Ministry on Monday claimed, without offering evidence, that Osama bin Laden's al-Qaida terrorist organization was involved.

Officials said 405 of the freed captives remained hospitalized, 45 of them in grave condition. Deputy Prime Minister Valentina Matviyenko said 239 people had been released.

Russian medical officials said 116 of the hostages held by Chechen rebels in a Moscow theater had succumbed to the gas, the exact composition of which remained a secret - even to medical personnel treating the victims.

Russian authorities provided the U.S. Embassy with some information about the effects of the gas, but have not told them the name of the agent despite repeated requests, an embassy spokesman said.

Doctors from a Western embassy have examined some of the former hostages and concluded "the agent they were exposed to appears consistent with an opiate rather than a nerve agent," the embassy spokesman said, speaking on condition of anonymity. Opiates, including morphine and heroin, are derivatives of the opium poppy.

In Germany, a physician treating two former hostages said doctors would try to determine what gas was used through blood and urine tests and that it did not appear to be a known chemical weapon.

"It remains a puzzle," said Dr. Thomas Zilker, a toxicology professor at Munich University Clinic.

The U.S. Embassy spokesman also said American diplomats located a body believed to be that of a U.S. citizen who died during the hostage-taking, one of two Americans in the theater when Chechen rebels stormed it Wednesday night during a performance of the musical "Nord-Ost."

Two foreign women - one Dutch, one Austrian - and a 13-year-old girl from Kazakhstan also were known to have died.

Russian officials said 50 rebels were killed during the storming of the building early Saturday. Many of the insurgents were women who claimed to be Chechen war widows.

As pressure grew on Russian authorities to identify the gas used in the raid, some lawmakers and commentators criticized the government.

Boris Nemtsov, a leader of the liberal Union of Right Forces party, criticized authorities for failing to treat the hostages promptly after pumping the gas into the theater.

"Why after special services brilliantly carried out the operation were there not enough ambulances, doctors and intensive care equipment? Why was medical aid not given on the spot?" he said on Russian television, referring to the fact that many victims were carried and dragged out of the building and put on buses to local hospitals.

At a Moscow hospital where many of the freed hostages were taken, a crowd of relatives waited to visit loved ones. Every time guards opened the black gates for ambulances or departing patients, the crowd rushed the entrance, pleading to be next.

"I don't like to complain, I know that we were lucky," said Valery Yegorov, waiting with a bouquet of yellow flowers to visit his daughter, Lena.

Hundreds of people - some weeping openly - placed flowers and candles in a cold rain near the theater in a rundown neighborhood in southeast Moscow. Police kept a tight cordon of metal barriers and military trucks around the building.

Some mourners said they felt authorities had done all they could to protect lives.

"There was no other way," said retiree Lyudmila Yemelyanova, expressing the sentiments of many who came to pay respects. "If the explosives inside the building had gone off, then not only the theater but all the neighboring buildings would have been destroyed."

The attackers burst into the theater Wednesday night, some with explosives strapped to their bodies. They mined the theater and threatened to blow it up unless Putin withdrew Russian troops from Chechnya.

Russian forces pulled out of Chechnya after a devastating 1994-1996 war that left separatists in charge but returned after rebels attacked a neighboring region and were held responsible for apartment bombings that killed about 300 people.

In 1995 and 1996, rebels seized hundreds of hostages in two raids in near Chechnya that were similar in scale to the theater assault but far from Russia's capital. Dozens of people died in both - many killed when Russian forces attacked the hostage-takers.