Istanbul police chief Celalettin Cerrah said the security forces determined that Thursday's explosion in an Internet cafe in the city, which killed one person and injured 15 others, was a bomb attack, Anatolia news agency reported.

The Kurdistan Freedom Falcons (TAK), a shadowy group the authorities say is linked to the separatist Kurdistan Workers' Party (PKK), claimed responsibility for the blast, according to a news agency close to the rebels.

The explosion ripped through the cafe, located behind the local headquarters of the riot police and frequented by officers, blowing out the windows of nearby buildings.

The owner of the cafe died in hospital. Seven of the injured were policemen.

The security forces are beefing up measures against possible PKK attacks on government buildings ahead of the anniversary of the capture of the group's jailed leader Abdullah Ocalan, Cerrah said.

Ocalan was captured on February 15, 1999 while on the run in Kenya. The anniversary of his arrest is usually marked with violent Kurdish protests.

Ocalan was condemned to death in June 1999, but his sentence was commuted to life in prison in 2002 after Turkey abolished capital punishment to catch up with European Union norms.

The Kurdish conflict has claimed some 37,000 lives since 1984 when the PKK, blacklisted as a terrorist organization by Ankara, the EU and the United States, took up arms for self-rule in mainly Kurdish southeastern Turkey.

Turkish officials say TAK is a cover group for the PKK, which is seeking to avoid international condemnation for attacks on civilian targets.