Two Europeans and three Turks were killed in the bombing

Earlier the UK ambassador told the BBC the Turkish authorities believed the PKK were responsible for the bombing on the tourist bus in which five died.

Turkish police has now tightened security at coastal holiday resorts.

The minibus blast came six days after a bombing in the nearby town of Cesme, which left at least 20 people injured.

One statement, carried on Sunday by the Mesopotamia news agency based in Germany, said it was from the armed wing of the PKK and that it had nothing to do with either the bombing or with a splinter organisation which has admitted similar attacks.

On Saturday the same agency carried a statement from a PKK commander, Zubeyir Aydar, condemning the bombing.

Neither statement can be independently verified.

No group has yet claimed responsibility for Saturday's blast, which Turkish officials suspect may have been caused by a parcel bomb, not a suicide bomber as first believed.

Violent campaign

Kurdish militants claimed responsibility for the Cesme attack, as well as one in Kusadasi in April, in which one policeman was killed and four other people were wounded.

Militants both from the far left and from Islamist circles have carried out bombings in Turkey in the past, as have Kurdish rebels.

The PKK, considered a terrorist organisation by the US and EU, has been staging a violent campaign against the Turkish government for an independent Kurdish state since 1978.

More than 37,000 people have been killed in the campaign.

The rebels declared a unilateral truce in 1999, but ended it in 2004, saying Turkey had not done enough to meet their demands.