Russian authorities have ordered security forces on high alert after receiving information from foreign officials pointing to the threat of a terrorist attack on public transportation, officials said Tuesday.

Authorities were checking information about the potential threat, they said.

A federal anti-terrorism headquarters received information "from foreign partners ... about the possibility a subversive terrorist act could be committed on ground transport and in the metro," according to a statement confirmed by a Federal Security Service official who said he was not authorized to give his name.

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Federal Security Service chief Nikolai Patrushev, who also heads the anti-terror center, ordered anti-terror forces on high alert and called for stepped-up measures to prevent any attack, the statement said. It offered no details on the nature of the threat or the measures to be taken.

It was unclear what country the information about the potential threat came from; Russia cooperates against terrorism with countries around the world, including the United States.

The statement did not say whether the threat was limited to any particular location in Russia, where several cities have subway systems. Security was stepped up in Moscow's extensive subway, including by increasing the number of teams with bomb-sniffing dogs, the RIA-Novosti news agency quoted a Moscow police official as saying.

The statement, read in part during news programs on state-run television, urged Russians to be alert and to cooperate with law enforcement authorities and inform them of anything suspicious.

It said the warning was received by the Federal Operative Headquarters, which is under the auspices of the National Anti-terrorism Committee, a body created by President Vladimir Putin early last year to coordinate anti-terror efforts.

The potential threat was discussed at a meeting of the headquarters Tuesday and law enforcement agencies gave reports on measures they were taking to avert an attack, the statement said. That suggested the information was received earlier, but it was unclear when.

Patrushev and other Russian security officials often announce that authorities have averted bomb blasts or other terror attacks.

The headquarters urged organizations and companies involved in public transport to help ensure the security of passengers.

Several bombings have occurred in the Moscow subway system and on ground transport in the capital and elsewhere during more than 12 years of conflict in mostly Muslim Chechnya, where large-scale fighting ended years ago but an insurgency continues. Separatist rebels from Chechnya and other restive parts of southern Russia's troubled Caucasus region have claimed responsibility for or been blamed for most of the many terrorist attacks that have plagued the country.

The Chechen rebel warlord who was behind many of the deadliest attacks, Shamil Basayev, was killed last July.

In August 2004, a suicide-bombing just outside a Moscow subway station killed 10 people. The next day, militants seized a school in the southern town of Beslan near Chechnya, beginning an ordeal that led to the deaths of 334 victims, many of them children.

In February 2004, an explosion ripped through a Moscow subway car during rush hour, killing 41 people, and a suicide bombing on a commuter train in the south in December 2003 killed 44. Six people were killed in two blasts on the same railway line that September.

A bombing in a Moscow subway car in June 1996 killed four people and two subsequent explosions on Moscow buses injured 33. In August 2000, a bomb exploded at a crowded pedestrian underpass that leads to three central Moscow subway stations, killing at least 12 people.

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