Russian President Dmitry Medvedev lays flowers on a subway platform Monday at Lubyanka station in Moscow, which was earlier hit by an explosion. Vladimir Rodionov/RIA Novosti/Associated Press)

World leaders are condemning the suicide bombings that occurred in Moscow's subway system Monday morning, killing 38 people and injuring dozens more.

Russia will "continue the fight against terrorism unswervingly and to the end," Russian President Dmitry Medvedev vowed Monday, shortly after the attacks.

Prime Minister Vladimir Putin, who built much of his political capital by directing a fierce war against Chechen separatists a decade ago, also said Monday that "terrorists will be destroyed."

Commuters injured by a bomb blast at the Park Kultury subway station in Moscow wait for medical care just outside the station shortly after the explosion Monday. (Egor Barbatunov/Associated Press)

U.S. President Barack Obama told Medvedev by phone that the U.S. was ready to co-operate with Russia to help bring to justice those who were behind what he called "heinous terrorist attacks."

And Canadian Foreign Affairs Minister Lawrence Cannon said Canada "strongly condemns the cowardly attacks."

No group has claimed responsibility for Monday's attacks, but Alexander Bortnikov, the head of Russia's security agency, suggested that the attacks could be connected to the restive Caucasus region that includes Chechnya.

Bortnikov said the assessment was based on fragments of the bombers' bodies. He did not provide any additional details.

Rush hour attack

Two female suicide bombers targeted two different stations during morning rush hour, police said.

The first blast hit around 8 a.m. local time at the Lubyanka station in central Moscow. The station is beneath the building that houses the main offices of the Federal Security Service, or FSB, the KGB's main successor agency.

About 45 minutes later, a bomb went off at Park Kultury station, near Gorky Park.

In both cases, the bombs were detonated as the doors opened after the train pulled into the station, police said.

Shortly after the blasts, emergency officials told Russian news agencies that more than 100 people were injured, but they didn't provide a breakdown of casualties at each station.

Police officers direct people from Park Kultury subway station. The blasts occurred aboard crowded trains in the middle of Moscow's busy rush hour. (Pavel Golovkin/Associated Press)

Media reports released later suggested the number of wounded was closer to 65.

Igor Serebryany was in a train travelling through Park Kultury station in the opposite direction after the blast.

"When our train arrived at Park Kultury on the opposite track across the platform, there was a wreckage of the train," he said.

"We were obliged to leave the station as soon as possible and the station was packed with policemen and special forces."

Police and security officials are reviewing surveillance footage after reports suggested the women may have had accomplices when they entered the stations. It's not clear whether the suspected accomplices were men or women.

Moscow's subway network is one of the world's busiest, carrying about seven million passengers on an average weekday. Both stations were reopened late Monday afternoon, officials said.

Chechnya link probed

Last week, Russian police killed an Islamic militant leader in the North Caucasus region, where security officials have been clashing with militant forces.

The killings have raised fears of retaliatory strikes, and in February Chechen rebel leader Doku Umarov warned in an interview on a rebel-affiliated website that "the zone of military operations will be extended to the territory of Russia ... the war is coming to their cities."

Umarov also claimed his fighters were responsible for the November bombing of the Nevsky Express passenger train that killed 26 people en route from Moscow to St. Petersburg.

The last confirmed terrorist attack in Moscow took place in August 2004, when Chechen rebels claimed responsibility for an attack on the subway system.

With files from The Associated Press