MOSCOW — An explosion believed to have been caused by a bomb ripped through a subway station next to the office of Belarus’s authoritarian president on Monday evening, killing at least 11 people, wounding more than 100 and worsening an already tense political situation there.

No one immediately claimed responsibility for the explosion, in Minsk, the Belarus capital, but witnesses described being hit by a wave of shrapnel that they said was contained in a bomb. Several victims’ limbs were torn off by the force of the blast, paramedics said.

The president, Aleksandr G. Lukashenko, indicated that he believed the explosion was terrorism. Prosecutors said an inquiry was focusing on a bomb.

Investigators and witnesses said the blast occurred on a platform just as passengers were leaving a train in the Oktyabrskaya station about 6 p.m., at the height of the evening rush. The station, in the center of Minsk, is very close to major government offices, including Mr. Lukashenko’s, as well as to his official residence.