Protestors set fire to rubbish bins and tyres in the southern town of Mersin, blocking streets in support of jailed PKK leader Abdullah Ocalan, the Anatolia news agency said.

Riot police retaliated with tear gas, charging the blockade in armoured vehicles and making a number of arrests, it said.

Masked demonstrators had attacked a bus with a Molotov cocktail in Mersin on Saturday before being pushed back by police. There were no casualties reported.

Police arrested three people in the southeastern town of Sanliurfa after a group of PKK supporters threw a Molotov cocktail at a bulldozer.

A group of masked men burnt three cars in an Istanbul suburb after attacking them with the home-made incendiaries.

Lawyers earlier this month said that Ocalan was being slowly poisoned in jail, citing laboratory tests which indicated abnormally high levels of toxic substances.

Ocalan, who led a bloody separatist rebellion in southeast Turkey from 1984 until his capture in 1999, is experiencing breathing and skin problems as well as severe pain which is interrupting his sleep, lawyers said.

The Turkish government denied the claims and sent a team of toxicologists to Ocalan's maximum-security island prison on Imrali, northwestern Turkey, which is still to publish its findings.

Sunday's clashes came hours after security forces killed a Kurdish rebel near the Syrian border and seven PKK members were found dead in neighbouring Diyarbakir.

The PKK, which is considered a terrorist organisation by the Turkish government, the European Union and the United States, announced a unilateral ceasefire in October 2006.

Ankara rejected it but the fighting, which has seen more than 37,000 people killed since the PKK's armed campaign began in 1984, has reduced since then.