At least seven people were killed on Monday in a blast at a metro station near Belarus President Alexander Lukashenko's office in Minsk, says television report.

Ninety people were wounded, of whom 50 were sent to hospitals in the Minsk area and 35 were given treatment on the spot, Minsk channel STV added.

The blast left clouds of suffocating smoke inside the city's busiest metro station, whose exits lead to both the strongman president's main office and his residence as well as the country's powerful Security Council.

Television footage from the Oktyabrskaya station showed dozens of people crowded into the smoke-filled station, which connects the city's two underground train lines.

Several were leaning back against the heavy stone columns, their faces bloodied by shrapnel, looking around in a daze.

"There was a lot of smoke, the glass of the train carriage shattered, and we were even scared that we would suffocate," one eyewitness said. "Everything went very quickly."

At least one person had both legs maimed by the blast, a witness said.

A reporter said that underground traffic had ground to a halt across the city of 1.8 million, which has never experienced a deadly attack.

Officials were careful not to speculate on the possible cause of the explosion, which came amid rising political tensions inside the country following Lukashenko's controversial re-election last year.

But underscoring the seriousness with which the government was treating the incident, Lukashenko was immediately briefed by his top advisers and was expected to hold a top-level security meeting later on Monday.

"This evening the head of state will hold an extraordinary meeting in connection with the explosion on the capital's metro," Lukashenko's chief spokesman Pavel Lyogky said.

The meeting was to include the head of the country's KGB security service, the city's mayor and heads of all the city's police departments as well as other senior officials, news reports said.

The explosion comes amid growing political tensions inside Belarus linked to the trials of opposition members who rallied against Lukashenko's December 19 re-election.

Tens of thousands of people demonstrated through central Minsk on election night after Lukashenko's overwhelming victory was announced, with truncheon-wielding police moving in against the protesters and arresting hundreds.

The arrests have added to the Lukashenko regime's growing international isolation, with both the European Union and the United States announcing travel bans and economic sanctions against some Belarussian state companies.

However despite the political unrest, Belarus is normally considered a safe country and has never been touched by large-scale militant attacks such as those carried out by Islamist militants in Moscow.

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.

In January this year, 37 people were killed in a suicide blast at Moscow's Domodedovo airport.

The man who claimed those attacks, Russia's most wanted Islamist rebel Doku Umarov, whom the Russian authorities hoped to have killed in an air strike last month, is alive and preparing reprisals, according to an audiotape released last week.