In a statement, the Prime Minister of the Czech Republic Petr Necas said he was "deeply hit by the tragedy of the gas explosion", the Associated Press reports.
It is not certain what caused the blast in Divadelni Street in the central Prague but it was likely to be a natural gas explosion, police spokesman Tomas Hulan said.
More top news
Ex-football manager Harry Redknapp told undercover reporters his own players bet on the result of one of their own matches, it is claimed.
A soaking then sunshine this weekend
As Hungary prepares to vote in a referendum on the EU's resettlement of refugees, thousands of migrants remain in limbo on the border.