The blast which tore through a rush-hour Minsk metro station on Monday was a terrorist attack, prosecutors said.
At least 11 people were killed and scores injured when a bomb exploded as a train stood at the Oktyabrskaya metro station at 5.55 pm (14:55 GMT).
The station is near the offices of President Alexander Lukashenko, who arrived at the scene shortly afterwards.
At a meeting with officials, Lukashenko called the blast “a serious challenge” to the nation.
“I don’t exclude that this gift could have been brought to us by outsiders. But we have to look at ourselves as well,” he said.
“Who gained by destroying the calm and stability in the country?” he asked. “Who did not like the stability in Belarus?”
He told the KGB - as the country’s security services are still known - to “turn the country upside down” to find those guilty.
He also informed the country's defense minister to check all military warehouses for missing explosives.
There is as yet no information on the cause of the explosion, the first ever in the Minsk metro.
Lukashenko, who has ruled Belarus since 1994, won disputed presidential polls last December Dozens of opposition figures, including political rivals were arrested after violent protests in Minsk following the announcement of the result.
While Belarus has been free of the Islamist terrorist violence that has plagued neighboring Russia, some 50 people were injured in July 2008 when a bomb went off at an independence day concert that Lukashenko was attending.
Russian President Dmitry Medvedev called Lukashenko to offer both condolences and assistance to the former Soviet republic. The Belarusian leader said later that Russian experts would arrive on Tuesday to help the KGB with the investigation.
Russia will send a team of experienced doctors to Minsk to help Belarusian metro station blast victims, a spokesman for Russian health and social development ministry said.
"The ministry is now forming a team of experienced doctors, who had worked in emergency situations. They will fly to Belarus to provide their Belarusian colleagues with assistance and advice," the source said.
The team will comprise neurosurgeons, intensivists and doctors specializing in blast-related injuries. Many members of the team treated victims of last year's twin blasts in Moscow metro.
MINSK, April 11 (RIA Novosti)