(Updates number of wounded, adds police confirmation, details) By Osman Orsal ISTANBUL, June 10 (Reuters) - A bomb blast outside a store in Istanbul wounded 14 people on Sunday, Turkish police said, amid increased worries about Kurdish separatist violence. The state Anatolian news agency said the blast appeared to have been caused by a percussion bomb, often used by Kurdish militants and other radical groups operating in Turkey. Authorities have warned of possible PKK attacks on civilian and security targets in cities and towns, especially in the run-up to national elections on July 22. "It is still not certain what kind of bomb it was," Istanbul police chief Celalettin Cerrah told reporters at the scene of the explosion. Percussion bombs typically make a loud noise but rarely cause serious damage. "The explosion was very powerful. We were really shaken," . said Muttalip Erdogan, who sells doner kebabs. The blast, which shattered the windows of many shops and offices, occurred in the Bakirkoy district of Turkey's largest city, near the airport, where Kurdish militants have carried out similar attacks in the past. Tensions are running especially high amid increasing clashes between Turkish troops and guerrillas of the banned Kurdistan Workers' Party (PKK) in mainly Kurdish southeast Turkey. The clashes have fuelled talk of a possible major Turkish army incursion into northern Iraq to attack PKK bases there. In May, eight people were killed when a suicide bomber struck a shopping mall in the capital Ankara. Authorities blamed that attack on the PKK, though the group denied involvement. Last week, seven paramilitary policemen were killed when PKK rebels attacked their base in the eastern province of Tunceli. On Saturday, three soldiers were killed when rebels remotely detonated a landmine near the Iraqi border. Each incident has added to pressure on the government, which faces a strong nationalist challenge in the election, to get tougher with the PKK. Ankara blames the PKK for the deaths of more than 30,000 people since it launched its armed campaign for an ethnic homeland in southeast Turkey in 1984.
