(CNN) -- Female suicide bombers detonated explosions that rocked two subway stations in central Moscow during rush hour on Monday morning, killing dozens of people, officials said.
A Web site associated with Chechen separatists, who have long fought for independence from Russia, claimed responsibility for the attacks. Immediately after the explosions, officials had cast suspicion on the separatists.
Chechnya is a southwestern Russian republic, in the Caucasus Mountains region. Years of conflict have been devastating for its infrastructure.
Chechnya's population of 600,000 to 800,000 is primarily made up of Sunni Muslims and Russian Orthodox Christians. Thousands have been killed and 500,000 Chechen people have been displaced in their conflict with Moscow. Below is a timeline of the conflict.
August 2009 - The head of a humanitarian agency in Chechnya and her husband are found dead, their bodies stuffed in the trunk of their car.
July 2009 - A leading human rights activist is abducted and killed near her home in Grozny. Natalya Estemirova, of the Russian human rights group Memorial, had openly criticized Chechnya's authoritarian president, Ramzan Kadyrov, and his methods.
April 2009 - Russia declares an end Thursday to its 10-year anti-terror "operation" in Chechnya with the rebel movement largely quashed. The end to the offensive could see the withdrawal of thousands of troops from the Muslim-majority region.
April 2007 - Eighteen people are killed when a Russian-made Mi-8 military transport helicopter crashes in Chechnya. Local media reports said the helicopter was shot down by Chechen rebels during a Russian operation.
September 17, 2004 - In an e-mail message posted on the Chechen rebel Web site, Kavkazcenter.com, Chechen terrorist leader Samil Basayev claims responsibility for several recent terrorist attacks in Russia, including the Moscow metro bombing, explosions aboard two passenger jets and the taking of hostages at a school in Beslan.
September 5, 2004 - The Russian government has one suspect in custody. The death count stands at 335 hostages, including 156 children, along with 26 hostage-takers and 10 Russian special forces soldiers.
September 3, 2004 - Russian troops end a standoff at Beslan, a Russia school in which Chechen rebels had taken several hundred students, teachers, and parents hostage.
September 2, 2004 - Some Beslan hostages are released.
September 1, 2004 - Armed attackers storm a school and herd at least 100 children, parents and teachers -- possibly as many as 400, later revealed to be 1,200 -- into a school in southern Russia where they threatened to kill the children. The hostage takers reportedly demanded the release of more than two dozen prisoners picked up during raids on Chechens in southern Russia in June and a Russian withdrawal all of its forces from Chechnya. Some of the hostage-takers were reportedly wearing explosives belts used in suicide bombings.
August 31, 2004 - A female suicide bomber kills nine people and herself, and wounds 51 others when she detonates a bomb outside a subway station in northeastern Moscow.
August 24, 2004 - Two Russian passenger planes are blown up almost simultaneously, killing 89. Federal Security Service are focusing on whether acts of terrorism brought down the jets after traces of Hexogen are found in wreckage of planes. Hexogen, a powerful military explosive, has been used by Chechen rebels in other bombings.
May 2004 - Akhmad Kadyrov, the president of Chechnya, is assassinated. Kadyrov was elected Chechen president with very strong backing from the Kremlin.
February 2004 - 40 are killed and 100 injured when a suicide bomber detonates a bomb on a Moscow metro train.
June 2003 - A suicide attack kills 15 people at a concert in Moscow.
May 2003 - 59 people are killed when two suicide bombers drive a truck full of explosives into a government complex in northern Chechnya.
March 2003 - A referendum upholds the new constitution for Chechnya.
October 2002 - Chechen rebels seize a theater in Moscow, and hold over 700 people hostage. Russian forces use gas to neutralize resistance; most of the rebels and 120 hostages are killed.
July 2000 - Guerrillas launch five suicide bomb attacks on Russian security bases. The deadliest attack kills 54 people.
February 2000 - Russian forces take control of Grozny, and the conflict begins to wind down.
September 1999 - Apartment buildings in Moscow, Buynaksk and Volgodonsk are bombed, resulting in the deaths of nearly 300 people. All of the bombs used were found to contain hexogen.
August 1999 - Islamist rebels launch incursions into neighboring Dagestan. Russian forces respond by moving into Chechnya in September.
August 31, 1996 - A peace accord is signed and Russian troops soon withdraw.
May 1996 - A cease-fire is declared, but fighting continues. Chechen rebels seize key government sites.
June 1995 - Chechen rebels kill over 100 hostages in a Russian town.
February 1995 - Grozny falls to Russian forces.
1994 - Russia sends 35,000-40,000 troops in to Chechnya to stop the rebellion.
1991 - Chechnya begins fighting for independence from Russia. Moscow sends troops in, but withdraws them after a few days.