At least 12 Kurdish separatist fighters and five members of the Turkish security forces have been killed in clashes in the southeast of the country, the army said.

Two separate attacks by suspected members of the Kurdistan Workers' Party (PKK) in Siirt province left two soldiers and three village guards dead, according to an army statement.

Twelve fighters were killed in the ensuing operation late on Wednesday, backed by artillery fire and helicopter gunships, the statement added.

Television news channels showed helicopters firing on rebel positions in the mountains near the town of Pervari in Siirt.

"In a co-ordinated effort, 12 terrorists were killed and their weapons were confiscated by reinforcements sent to the region," the army said.

Tougher measures

The violence is a further sign of rising tension in the troubled region, where the PKK is fighting for an independent Kurdish state.

More than 50 Turkish soldiers have been killed in recent months as the PKK has increased attacks on military installations in the primarily Kurdish southeast.

The military says 42 PKK were killed in clashes in June.

The Turkish government has come under pressure to take tougher measures against the group, which is considered a terrorist organisation by the European Union and United States.

The PKK stepped up attacks on the military after calling off its one-year truce on June 1, dissatisfied with prime minister Recep Tayyip Erdogan's concessions to Kurdish demands for reform.

Many of the rebels stage hit-and-run attacks from bases in northern Iraq.

The PKK took up arms against Turkey in 1984 in a bid to carve out an independent Kurdish state.

The conflict has claimed the lives of more than 40,000 people, mainly Kurds, and has led to gross human rights violations on both sides, displaced thousands and impoverished the region.

Recent clashes have cast a shadow over government efforts to boost Kurdish freedoms and investment in the impoverished southeast in return for the PKK to lay down arms.

Earlier this month, the PKK said it was ending a unilateral ceasefire in place since April 2009 because of continuing Turkish military operations, and last month jailed PKK leader Abdullah Ocalan said he was abandoning efforts to seek peace with Turkey.