The attack in the capital early on Thursday came as Bulgaria tries to prove to the European Union that it can fight high-level corruption and organised crime. The EU will decide on May 16 whether to let the Balkan state join in 2007 or delay it by a year.

The journalist, Vasil Ivanov, said he believed that the bomb was intended to kill him because of investigative reports in which he uncovered a number of acts of fraud, inmate abuse at prisons, and other crimes.

"My family was inside and it's a wonder nobody was injured, because all the walls on the floor are smashed," Ivanov told Nova Television, where he works.

He said he would not stop producing his reports, the latest of which uncovered prisoner abuse at Sofia Central prison.

Organised crime

Ivanov's station and poiticians from the ruling Socialist-led coalition condemned the attack.

The politicians said in a statement: "It is disturbing that this happened when the country's security is at the centre of our EU partners' attention. Not only the home of a journalist was bombed, but freedom of speech was threatened.

"We have the necessary political will to work to guarantee the safety of Bulgarian citizens and the country."

Bulgaria has promised Brussels that it will jail senior officials who have made corrupt deals and convict organised crime bosses who diplomats say control large parts of the economy.

Gangs have killed scores of people in shootings and bombings since 2001, but authorities have yet to convict a single suspect for any of the murders.