Moscow ? At least 40 armed Chechen rebels stormed a crowded theater and took hundreds of people hostage in the midst of a musical, threatening early today to shoot their captives and blow up the building if Russian security forces attacked.

A loud explosion was heard about 9:15 a.m. today, but it was not clear whether it came from inside the theater, or what caused it. The building did not appear to have been damaged.

Several hours after rebels rushed the theater, firing automatic weapons, they began communicating with Russian officials by cell phone. The hostage-takers demanded that Russia end the war in Chechnya, a southern region where the army is fighting Islamic separatists.

The talks eventually halted, and police appealed to the hostage-takers to answer their phones.

Some hostages released by the male and female rebels reported seeing pools of blood. But there was no confirmation of casualties at the theater in a working-class neighborhood of southeastern Moscow, about three miles from the Kremlin and the Red Square.

The rebels had automatic weapons, grenades, belts with explosives attached, mines and canisters of gasoline, lawmaker Yuli Rybakov said outside the theater. There was little water or food inside, he said. The raid occurred in wet, freezing weather.

One hostage told Echo of Moscow radio that the hostage-takers attached explosives to theater chairs, columns and walls, along the aisles, and to their own bodies.

The gunmen told national parliament member Aslanbek Aslakhanov from Chechnya, who was serving as a mediator, that they wanted Russian troops to withdraw from Chechnya and implement a cease-fire, he said. A pro-rebel Web site said Russia had seven days to begin its withdrawal or the theater and hostages would be blown up.

A freed hostage walks with her hands up after being let out of a Moscow theater that was seized by armed men. Chechen rebels on Wednesday took hundreds of audience members hostage and demanded that Russia end its war in Chechnya within a week.

Battle line moved

The raid brought home to the very heart of Russia a war seen as far-off by many Russians despite a growing number of military and civilian casualties. The Russian military has been especially tough on rebels, but several hostages, speaking by cell phone to Russian reporters, appealed to security forces not to use force in the Moscow siege.

“There are women, children, foreigners in here,” cardiologist Maria Shkolnikova told REN TV. “We don’t want the building to be stormed.”

She said hostage-takers had lost family members in the war.

Russian security forces do not intend to storm the building unless the hostage-takers start killing their captives, said Gennady Gudkov, deputy chairman of the parliamentary Committee on Security. It could be days before the situation was resolved, he said, adding that 711 tickets were sold for the performance.

Schools and kindergartens near the theater were closed and nearby hospitals prepared for any casualties.

Automatic weapons fire rang out on at least four separate occasions. Security forces were on high alert throughout the Russian capital and around power plants after the audacious attack, which appeared to be meticulously planned.

The drama was a blow for President Vladimir Putin, who repeatedly has said Russia has the Chechnya situation under control. Putin scrapped planned trips today to Germany and Portugal, his spokesman, Alexei Gromov, said It was unclear whether Putin would attend a weekend summit in Cabo San Lucas, Mexico.

While Putin’s popularity remains high, recent opinion polls show declining public support for the war.

Foreigners among hostages

Moscow police spokesman Valery Gribakin said about 40 to 50 rebels were in the theater and they had released 100 women and children from the theater. The freed hostages were distraught, sobbing and shaking as they emerged from the building where they were watching a popular musical based on a romantic novel.

Members of the Chechen community in Moscow have volunteered to replace the hostages, especially children, Gribakin said.

The German Foreign Ministry confirmed there were Germans inside, while the Austrian ambassador was at the scene inquiring about an Austrian woman inside. Russian news reports said three British citizens and one Dutch national also were inside.

In Washington, the White House said it was not aware of any Americans being held.