President Dmitry Medvedev on Friday urged security forces to remain vigilant in the face of terrorism, a day after a female suicide bomber blew herself up in North Ossetia's capital, Vladikavkaz, killing 12.

Addressing security officials in St. Petersburg, Medvedev said that while terrorist activity had largely been contained in the country, the Vladikavkaz bombing "showed that a terrorist threat remains."

"We cannot let our guard down," Medvedev said in televised remarks. "Although terrorist acts have been suppressed, the environment for such crimes exists."

A total of 12 people were killed and 41 injured in Thursday's attack, Investigative Committee spokesman Alexander Bastrykin said. Seven people were killed in the blast, while five died in the hospital, he said.

The bomber blew herself up near a busy market in downtown Vladikavkaz. It was the first terrorist attack targeting civilians since Medvedev assumed the presidency six months ago and the first to involve a female suicide bomber since the 2004 school attack in Beslan, also in North Ossetia.

Investigators believe that the bombing may have been an attempt to destabilize the situation in the North Caucasus or exacerbate Ossetian-Ingush relations, Bastrykin said.

Bastrykin said all of the victims in the blast had been identified, though the bomber's identity had yet to be established.

"The main thing is that it was possible to gather the remains of the woman who probably blew up the bus," he said, Interfax reported.

Eyewitnesses to the explosion described the suspected suicide bomber as an Ingush woman aged 40 to 45, Interfax reported, citing a law enforcement source.

Officials from the Federal Security Service and the Interior Ministry could not be reached for comment. Calls to regional and local prosecutors in Vladikavkaz went unanswered Friday.