Belarus on Tuesday hunted the perpetrators of the Minsk metro bombing that killed 12 as President Alexander Lukashenko pointed to a foreign link in the first deadly attack in its modern history.

The explosion at a busy metro station in the heart of the Belarussian capital near the headquarters of Lukashenko stunned a city which has never seen attacks like those suffered in neighbouring Russia.

Authorities described the attack in the early evening rush hour on Monday as an act of terror and said they were already pursuing a suspect. But officials seemed for the moment at a loss to explain the motive for the attack.

"As of 2:30 local time (23:30 GMT), the number of dead reached 12 people, six of whom have been identified," the country's security service, still known by its Soviet acronym KGB, said in a statement, raising a previous toll of 11.

A total of 149 people needed medical treatment, 22 of whom are in a serious condition, and 30 of whom have injuries of medium severity, the KGB statement said.

The blast came amid rising political tensions in the country following Lukashenko's controversial re-election on December 19, which sparked a massive opposition protest and a brutal crackdown on government critics.

Belarus, an ex-Soviet state between the EU and Russia, is also enduring severe economic crisis that has seen the government carry out a partial currency devaluation to preserve rapidly dwindling foreign currency reserves.

Lukashenko - a leader who was once dubbed Europe's last dictator by the United States and enjoys friendly relations with states like Iran - said he could not rule out a foreign hand in the attacks.

"Guys, we have been presented with a serious challenge. We need an adequate response - and it must be found," the strongman leader told a KGB meeting.

"I do not rule out that this is a present from outside but we must look at home too," he said. "Go and establish who could benefit from breaking the calm in the country," he told the KGB.

Belarus saw bomb blasts in 2005 in its western city of Vitebsk and in 2008 in Minsk. Both explosions, blamed on the nationalist fringe, wounded around 50 people but did not cause fatalities.

Lukashenko said the metro bombing and the July 2008 blast - at concert which he attended - could be 'links in one chain'.

Health Minister Vasily Zharko said that most of the injured had shrapnel wounds or had been thrown by the force of the blast, while the worst injured had limbs torn off.

The Prosecutor-General's office has opened a criminal investigation into an act of terrorism, the KGB statement said. "Information has been received about a probable perpetrator. He is being searched for," it added.

An explosive device packed with ball bearings and with a force equivalent to five to seven kilograms of TNT, was apparently hidden under a bench on the platform of the metro station, Interior Minister Anatoly Kuleshov said.

It was likely set off by remote control, a security source told the Interfax news agency.

At the time of the explosion, around 300 people were in the Oktyabrskaya station and another train was approaching in the opposite direction, which was ordered to run through without stopping, Kuleshov said.

Lukashenko visited the scene of the blast with his young extra-marital son Kolya, a boy who has become a talisman for the president and now accompanies him to almost all state events.

"We have been attacked, Crudely, cruelly and inhumanely," said the mass-circulation daily Belarus Sevodnya. "We Belarussians thought we could not have enemies. We were wrong," it added.

The interior minister said that all means of transport arriving and leaving the country were being searched and that security had been heightened at crowded places including rail stations and airports.

On March 29, 2010, 40 people were killed and dozens wounded by two female suicide bombers during the morning rush hour on the Moscow metro and 37 were killed in an attack on the Russian capital's main airport this year.