Turkey has continued its airstrikes against Islamic State extremists in Syria - but has now widened its anti-terror campaign to also hit Kurdish militant targets inside Iraq.

Fighter jets hit rebel shelters and storage facilities belonging to the rebel Kurdistan Workers Party, or PKK,in northern Iraq late on Saturday.

The United States has backed the actions, saying Turkey has the "right to defend itself" against attacks by the PKK.

White House spokesman Alistair Baskey condemned recent terrorist attacks by the PKK, which the US sees as a terror group, and encouraged them to renounce terrorism and resume talks with the Turkish government.

On Sunday morning it was reported that two Turkish soldiers had been killed and four others wounded in a bomb attack in southeastern Turkey which has been blamed on Kurdish rebels.

The fresh attacks come just a few days after Turkey launched assaults against Islamic State targets in Syria, as it continued its military response to a deadly wave of violence.

The PKK, which has been fighting Turkey for autonomy since 1984 and is also considered a terrorist organisation by Ankara, claimed a ceasefire in place since 2013 was now meaningless.

The group said on its website: "The truce has no meaning anymore after these intense air strikes by the occupant Turkish army."

The strike against Kurdish militants provoked protests in Turkey, Iraq and some European cities and it could also complicate the war, as the Kurds have been one of the main forces on the ground working to defeat IS.

Strikes across its borders have been accompanied by a domestic police crackdown, with nearly 600 suspected members of IS and the PKK being rounded up in raids across the country.

The escalation in military activity by Turkey comes after a suspected IS suicide bomber killed 32 people, some of them Kurds, in the border town of Suruc.

This triggered violence in the mainly Kurdish southeast, with the PKK killing two police officers, claiming it was retaliation for the suicide attack.

Many Kurds and opposition supporters accuse the regime of Turkish President Recep Tayyip Erdogan of secretly backing IS against Kurdish fighters in Syria, a charge strongly denied by the government in Ankara.

Prime Minister Ahmet Davutoglu has pledged to fight all "terrorist groups" equally and the country, previously reluctant to enter the fight, has also promised to allow the US to use key air bases to target IS.