Bulgaria has launched a crackdown on "untouchable" crime bosses, aiming to break organised crime's links to the state, its chief prosecutor said on Wednesday, promising to bring 300 gangsters to justice this year.

Boris Velchev said the arrest last week of members of a powerful crime gang was not a one-off but part of a drive to restore the rule of law -- key to regaining the trust of the European Union and securing aid flows to the Balkan country.

The European Union and the United States congratulated Bulgaria for the arrests, breaking up a crime ring suspected of more than a decade of money laundering, racketeering, bribery and tax fraud, under protection from corrupt authorities.

EU ambassadors wrote to the centre-right government, elected last July, saying convictions were now needed to regain the trust of Brussels which in 2008 cut Sofia's access to millions of euros in EU aid over fraud.

"We are confronting people who in the past 20 years seemed absolutely untouchable," Velchev told foreign media. "From now on, there won't be a tendency of convergence of organised crime with the state".

He said prosecutors aimed to take most of Bulgaria's estimated 300 major gangsters to court by the end of the year.

But it would not be easy to jail them, he said. "Their contacts with politicians, public servants, police are so big that they always surprise us."

Sofia is under great pressure to demonstrate results by July, when Brussels will assess its progress. Failure to show progress could threaten access to some of the 11 billion euros in EU aid promised to the bloc's poorest nation for 2007-2013.

Tough-talking Prime Minister Boiko Borisov, a firefighter by training, said last week his cabinet had declared a war on organised crime to end a climate of impunity that has reigned since communism collapsed twenty years ago.

In December, police arrested more than 25 people suspected of specialising in kidnapping the rich and famous. A senior interior ministry official was arrested earlier this week on suspicion of working for a crime group.

Prosecutors have also charged former ministers of agriculture and defence with abuse of power and are investigating an ex-labour minister for embezzlement.

But political analysts and newspaper commentators remain sceptical about whether crime bosses and corrupt high-level officials will actually be sent to jail.

Despite arresting and charging suspects in the past, Bulgaria has failed to convict a single senior official of corruption and has only jailed one crime boss since 1989.

Velchev, whose seven-year mandate started in 2006 and has since repeatedly asked for more time to show results, blamed Bulgarians' high tolerance to corruption and loopholes in laws for the country's poor track record.

"There is no way we can catch all the corrupt, and thank God, because if we caught them, we would be puzzled where to put them," he quipped, referring to Bulgaria's overcrowded prisons.

Reuters