ANKARA (REUTERS) - US President Barack Obama and Turkey's President Tayyip Erdogan pledged on Tuesday continued cooperation in the fight against terrorism, especially Islamic State in Iraq and Syria (ISIS) and Kurdistan Workers Party (PKK) militants, Turkish presidential sources said.

During his phone call to Erdogan, Obama also offered his condolences for last week's bombing in Istanbul, when 10 German tourists were killed in a suicide attack blamed on ISIS, and for an attack in the southeastern province of Diyarbakir carried out by the PKK.

The two leaders said the fight against terrorism would be among a number of topics on the agenda when US Vice President Joe Biden visits Turkey on Saturday.

Nato member Turkey, a member of the US-led coalition battling ISIS in Syria and Iraq, has increasingly become a target for the Sunni Muslim militants.

Prime Minister Ahmet Davutoglu blamed ISIS for the bombing on Jan 12 in Istanbul's historic heart. The suicide bomber is thought to have crossed recently from Syria.

ISIS is also believed to be behind other attacks last year in Turkey, including one in the capital Ankara in which more than 100 people were killed.

Turkey's predominantly Kurdish south-east is currently engulfed in the worst violence since the 1990s after the collapse last July of a two year-long ceasefire with PKK militants.

Last week, the PKK, deemed a terrorist organisation by the United States and the European Union as well as by Turkey, attacked a police station in a Diyarbakir district with a truck bomb, killing six people including a baby and two toddlers.