Police raided the Gebze offices of the pro-Kurdish Democratic Society Party (DTP) after seeing several "suspicious looking people" enter the building one day after Saturday's attack, the Kocaeli governor's office said in a statement carried by the Anatolia news agency.

It said 14 people, including Meral Kurum, the DTP chairwoman for Gebze, were detained.

The statement said police seized five petrol bombs along with documents and banners praising jailed Kurdish rebel leader Abdullah Ocalan, whose outlawed Kurdistan Workers' Party (PKK) has waged a bloody 22-year campaign for self-rule in southeast Turkey.

The DTP, Turkey's main Kurdish party, is frequently accused of supporting the PKK. Several of its members have been prosecuted for links with the group, which is blacklisted by Ankara, the United States and the European Union.