MOSCOW — Female suicide bombers set off huge explosions during rush hour Monday morning in two subway stations in central Moscow, officials said, killing at least 35 people and raising fears that the Muslim insurgency in southern Russia was once again being brought to the country’s heart.
The first attack occurred as commuters were exiting a packed train at the Lubyanka station, which is located near the headquarters of the F.S.B., the successor to the Soviet-era K.G.B. Officials said they suspected that the attack there was intended as a message to the security services, which have helped lead the crackdown on Islamic extremism in Chechnya and other parts of the Caucasus region in southern Russia.
The two explosions spread panic throughout the capital as people searched for missing relatives and friends, and the authorities tried to determine whether more attacks were planned. The subway system, known as the Metro, is one of the world’s most extensive and well-managed, and it serves as a vital artery for Moscow’s commuters, carrying as many as 10 million people a day.
“The terrorist acts were carried out by two female terrorist bombers,” said Moscow’s mayor, Yuri M. Luzhkov. “They happened at a time when there would be the maximum number of victims.”
Mr. Luzhkov said 23 people were killed in the first explosion, at the Lubyanka station, and 12 people were killed 40 minutes later in a blast at the Park Kultury station. Dozens were injured.
No one immediately claimed responsibility for the attacks.
Photos taken after the attacks showed scenes of devastation, with bodies strewn across subway cars and station platforms.
Pavel Y. Novikov, 25, an electrician, said he was evacuated from the Park Kultury station about 15 minutes after the explosion.
“It smelled like a burned rubber,” he said. “I saw blood, and I saw bloody clothes on the ground. It was so horrible.”
Kirill Gribov, 20, a university student, said he was on a train that arrived at the Park Kultury station just as the suicide bomber detonated her explosive belt on the train across the platform.
“The explosion was so loud that we all were deafened,” Mr. Gribov said. “Then I remember a cloud of gas coming from the blown train in front of us, colored in pink, maybe because of blood. Some people were in panic, some stood still, but all of us somehow found our way outside the station. It was only at the street when I realized what had just happened. Mobile service was blocked, I couldn’t even call my parents, and I had to walk several kilometers because of the traffic.”
President Dmitri A. Medvedev was briefed on the blasts by top law enforcement and security advisers. “Russia will fight terrorism without hesitation and to the end,” he said.
Prime Minister Vladimir V. Putin, who was traveling in Siberia, was also helping to coordinate the federal response.
In the early part of the last decade, the subway system was subjected to several attacks related to the separatist war in Chechnya. With the explosions on Monday, Muscovites expressed renewed concerns that they might again be targeted.
Officials said the first explosion on Monday occurred at 7:50 a.m. in second car of a train at the Lubyanka station, killing people both on the platform and inside the train.
The authorities closed off the station and the surrounding Lubyanka Square, formerly the site of the notorious Lubyanka prison, which was connected to the headquarters of the K.G.B.
About 40 minutes later the second attack took place, in the third car of a train at the Park Kultury station, officials said.
Yuri Syomin, the Moscow city prosecutor, said investigators believe that both explosions were set off by female suicide bombers wearing belts packed with explosives.
Crowds of people rushed to both stations in an effort to locate relatives, and cell phone networks became overloaded. The streets in central Moscow were blocked with traffic as people avoided the subway system.
The attacks marked the second major upsurge in terrorism on the transportation system over the last year. In November 2009, a bomb in a rural area derailed a luxury train traveling from Moscow to St. Petersburg, killing 26 people. The authorities have linked the attack to Muslim insurgents in the Ingushetia region, which is near Chechnya.
In February, a Chechen rebel leader, Doku Umarov, threatened in an interview on a Web site to organize terror acts in Russian population centers.
“If Russians think that the war is happening only on television, far from the Caucasus, and it will not touch them, then we are going to show them that this war will return to their homes,” he said.
The Russian government has sought to suppress violent Muslim extremism in the south since the fall of the Soviet Union in 1991.
Two brutal wars in Chechnya and a guerrilla insurgency gave rise to numerous bombings and acts of terror in southern Russia throughout the 1990s. Starting in 2002, Chechen separatists then began to export their bombing campaign to Moscow.
That October, a group of Chechen terrorists stormed into a Moscow theater during a performance and took some 850 actors, musicians and theatergoers hostage. After 57 hours of negotiations, Russian special forces launched an assault, killing all the militants and 117 of the hostages.
About 20 of the militants involved the theater siege were women, and several were wearing explosive vests. The following year, Chechen tacticians began using female suicide bombers in Moscow.
The first of those attacks came in July 2003, when the Russian authorities said a Chechen woman exploded a suicide belt at a rock concert, killing more than a dozen people. In what was to have been a coordinated attack, the police said, another woman’s explosives failed to detonate nearby.
In December 2003, a woman bomber blew herself up in central Moscow, killing six people and injuring dozens. She was identified as the widow of a Chechen guerrilla commander, and the female bombers soon came to be known in Russia as the “black widows.”
In September 2004, a suicide bomber killed at least 9 other people and wounded more than 50 outside the Rizhskaya subway stop. In February of that same year, a woman carrying a bomb destroyed another subway car, killing at least 41 people as the train moved between the Paveletskaya and the Avtozavodskaya stations at one of the busiest times of the day.