A group of radical Kurdish militants also claimed responsibility for a bomb attack Wednesday against an office of the ruling Justice and Development Party (AKP) in Istanbul in what it described as a reprisal attack for the unrest.

Two of the slain soldiers died while on patrol in the mountains of Sirnak province near Iraq when they stepped on a landmine planted by militants of the rebel Kurdistan Workers' Party (PKK), the local governor's office said in a statement.

Three others were shot dead in an ambush as security forces launched a search operation in the area to hunt down those responsible for the mine attack.

The statement said two PKK militants "were rendered ineffective" in the ensuing clash, without specifying whether they were killed or captured.

Separately, a policeman died from his injuries after PKK rebels opened fire with automatic weapons on a police station in the town of Genc, Bingol province, late Tuesday, hospital sources said.

More than 37,000 people have been killed since 1984, when the PKK -- considered a terrorist group by Turkey, the United States and the European Union -- took up arms for self-rule in mainly Kurdish southeast Turkey.

The latest deaths followed a week of violence that claimed 15 lives as Kurdish rioters clashed with security forces in the southeast and in Istanbul, in the worst urban unrest in the country for years.

Police opened fire to disperse the demonstrators, many of them teenagers and children, who torched banks and public buildings, vandalized shops and threw Molotov cocktails.

The victims included three women killed Sunday in Istanbul when a petrol bomb attack set a bus on fire, causing it to crash into another vehicle.

The Kurdistan Freedom Falcons (TAK), which police say is a cover group for the PKK, said Wednesday that it had placed a bomb at the AKP's office in Esenyurt district in Istanbul in revenge of the government's harsh response to the protests.

In a statement published on its website, TAK warned of fresh attacks if the government does not drop its policy of "repression" against the Kurds.

"The child murderers ... who are dealing massacre and death to our people ... will not be able to escape our reprisal units," the statement said.

"We will pursue acts against the fascist AKP and all fascist institutions which support and carry out the massacre of our people," it added.

Three people sustained slight injuries when the bomb placed in a garbage bin at the entrance of the office went off, a party official told AFP.

TAK has also claimed a bomb attack on an Istanbul bus station on Friday which killed a street vendor.

An AKP office in Kiziltepe, near the Syrian border, was ransacked Saturday when hundreds of Kurdish youths went on a rampage in the town.

Earlier Wednesday, officials said 10 kilograms (22 pounds) of plastic explosive of a type generally used by Kurdish militants were found at a cemetery in the same district where the bombed AKP office was located.

The government has accused the PKK of orchestrating the riots that first erupted on March 28 in Diyarbakir, the biggest city in the southeast, after the funerals of PKK militants killed in clashes with the army.

On Tuesday, Prime Minister Recep Tayyip Erdogan said Turkey would not give in to the violence, while pledging more democracy and welfare for the Kurds.