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.

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.

The ex-Soviet state of 10 million people is heavily policed and, though the bombing resembled similar attacks in Russia, it has no Islamic insurgency problem and no real history of political violence.

President Alexander Lukashenko, the autocratic leader who has led Belarus since 1994, said the explosion was an attempt to destabilize 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 defense 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.

'TIGHTENING OF SCREWS' FEARED

Lukashenko, at odds with the West over his authoritarian rule, linked the explosion to a previous unsolved blast in 2008, saying: "I do not rule out that this was a gift from abroad."

The blast occurred as Belarus struggles with a damaging run on foreign currency which has prompted panic-buying.

Central Bank foreign currency reserves are at their lowest in two years and there is no new credit deal with the International Monetary Fund in sight.

Lukashenko's re-election for a fourth term in December led to street protests that were broken up by police.

One opposition figure said he feared Lukashenko would use the blast to crack down even more harshly on political rivals.

"Regardless of who organized and ordered the blast, the government will be tempted to use it as an excuse to tighten the screws ... I am afraid they will use it," said Anatoly Lebedko, leader of the opposition United Civic Party.

Grigory Kostusev of the Belarussian People's Front, who ran against Lukashenko last December, told Reuters he thought the roots of the attack probably lay in Russia.

"The Belarussian special forces are not earning their bread. Unfortunately, they are very active when it comes to dealing with political rivals but they can not deal with a real threat from bandits," Kostusev added.

On Tuesday there was a reduced service running on Minsk's metro network and a heavy police presence at many stations.

People placed flowers and candles at the entry to Oktyabrskaya station in memory of the dead.

"I have a feeling of sadness and painful anger. This should not have happened to us. We are not the sort of country where this sort of thing happens," said Valentin Lepen, aged 70.

Belarus shares borders with EU members Poland, Latvia and Lithuania, and with Russia and Ukraine.

The European Union and the United States have imposed a travel ban on Lukashenko and his closest associates because of the December 19 crackdown. He has said the opposition rally was an attempted coup financed by the West.

The Organization for Security and Cooperation in Europe monitors said the vote count was flawed and criticised police for being heavy-handed. The remarks angered Minsk, which forced the OSCE to close down its office there.