Interior ministry officers check passengers at the entrance to the Kamennaya Gorka metro station in Minsk April 12, 2011. [Photo/Agencies]

MINSK- Police in Belarus carried out spot checks on roads and at stations and airports on Tuesday after a bomb blast tore through a crowded metro station in the capital Minsk on Monday evening, killing at least 12 people.

Related readings: 12 killed, 126 injured in Minsk metro blast

As police hunted those responsible for what appeared to have been a bomb activated by remote control, a top official from the prosecutor general's office described the attack as an act of "terrorism", unprecedented in Belarus.

President Alexander Lukashenko said the explosion was an attempt to destabilise the country.

"This is the first time we are encountering such a manifestation of terrorism," Deputy Prosecutor-General Andrei Shved was quoted as saying by Interfax news agency. But he gave no indication of who might have been behind it.

The defence ministry said 204 people were in hospital, 26 of them in a serious condition, after the evening rush-hour blast at Oktyabrskaya station, one of Minsk's busiest underground rail junctions close to the presidential headquarters.

Shved was also quoted as saying several people had been detained in connection with the attack, though it was not immediately clear whether they were real suspects in the affair.

The explosive device, which had been packed with metal ball bearings, nails and bolts and had a strength equivalent to 5-7 kgs of TNT, had apparently been left under a platform bench.

"We are not talking about suicide bombers. In all probability, it was a remote-controlled device," Shved added.

It blew up as a train came into the station and about 300 people were milling around.

Belarus's state security service raised the death toll to 12 after the death of one injured person overnight. Wednesday was declared an official day of mourning.