Devastation at Minsk metro; photo - EPA/PAP

UPDATED - Poland’s Foreign Ministry has sent condolences to Belarus, after what is thought to have been a terrorist attack in a metro station in Minsk, killing 12 and leaving over 100 injured, many seriously.

"My thoughts turn today primarily to those who have lost loved ones," Foreign Minister Radek Sikorski writes in a letter to his Belarusian counterpart, Sergei Martynov, sent Tuesday morning.

Belarus's Deputy Prosecutor-General Andrey Shved said midday today that several people had been held over the explosion, which authorities have described as a terrorist attack

The explosion occurred late afternoon yesterday at the busy Oktyabrskaya metro station, just 100 metres from the central offices and residence of President Aleksander Lukashenko.

Witnesses gave an indicator of the extent of the blast, describing seeing a crater where an escalator once was and part of a ceiling collapse.

Eleven people were pronounced dead immediately after the explosion, one more person has since died in hospital.

Belarus’s attorney general said he was launching a “terrorist” investigation last night, and President Lukashenko said that his administration would not rest until the perpetrators were caught and punished.

Foreign Minister Sikorski writes in his letter that “it is clear that the explosion was the result of a deliberate action,” and said he would like to express his “strong condemnation” of the attack on human life.

There has been rising tension in Belarus since the disputed presidential elections last December which observers from the US and EU have declared “rigged”.

But President Lukashenko said that “I do not rule out that the blast was a gift from abroad,” and linked the explosion yesterday to an unsolved attack at a concert in Minsk in 2008 where over 50 were injured.