(Adds number of injured, market reaction, details) By Seyhmus Cakan DIYARBAKIR, Turkey, June 15 (Reuters) - A bomb exploded at a bus station in the mainly Kurdish city of Diyarbakir in southeastern Turkey on Friday, injuring five civilians and a soldier, security officials said. The bomb targeted the city's busiest street and a bus station used by army and civilian transport. The region was already tense due to mounting clashes between Turkish troops and separatist Kurdistan Workers Party (PKK) guerrillas that have fuelled talk of a possible major Turkish army incursion into northern Iraq to attack rebel bases there. In recent weeks dozens of soldiers and civilians have been killed in suspected attacks by the PKK, which is considered a terrorist organisation by the United States, the European Union and Turkey. There was no claim of responsibility for the latest bombing. The police launched an operation in Diyarbakir -- the largest city in the restive southeast --after the blast and bomb experts tried to determine what type of explosive had caused it. Financial markets, rattled recently by the talk of an army incursion into Iraq, were largely unmoved by the bombing. Security officials, who declined to be named, said it was a time bomb that detonated earlier than planned, preventing a disaster. One person was seriously injured. In May, eight people were killed when a suicide bomber struck a shopping mall in the capital Ankara. Authorities blamed the attack on the PKK, though the group denied involvement. Turkish authorities say some 4,000 PKK rebels are based across the mountains in northern Iraq. Earlier this week the PKK announced a conditional ceasefire, although attacks continue. BUFFER ZONE Turkey's military has sent tens of thousands of troops, as well as tanks and other heavy military equipment, to the border area with Iraq -- a move which has worried the international community given the relative stability of northern Iraq. Turkey's top generals have urged the government to authorise a cross-border incursion, a move the United States opposes. Diplomats said the armed forces were also pushing for a possible 10-15 km (6-9 mile) deep buffer zone to be set up inside Iraqi territory by Turkish troops to prevent rebels from crossing. The army has not commented on such a move. "It (a buffer zone) will be effective and stop PKK infiltrations from northern Iraq but an agreement with Iraqi and U.S. officials is needed to do so," Turkish Daily News quoted retired Major Gen. Armagan Kuloglu as saying. Iraq's foreign minister urged Ankara on Thursday to rely on dialogue with Iraqi authorities, the United States and the regional government in the semi-autonomous Kurdish area of northern Iraq. Ankara blames the PKK for the deaths of more than 30,000 people since it launched an armed campaign for autonomy in southeast Turkey in 1984. Turkey is also suspicious of the regional government in northern Iraq. (Additional reporting by Selcuk Gokoluk in Ankara)
