Reuters, Washington :US President Barack Obama and Turkish President Tayyip Erdogan on Tuesday pledged continued cooperation in the fight against militants, including ISIS and Kurdistan Workers Party (PKK) militants, the White House and Turkish presidential sources said.During his phone call to Erdogan, Obama offered his condolences for last week’s bombing in Istanbul, when 10 German tourists were killed in a suicide attack blamed on Islamic State, the White House and Turkish presidential sources said.Obama also condemned a recent string of attacks by the PKK against Turkish security forces, and he stressed the need for de-escalation, the White House said in a statement.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 Islamic State in Syria and Iraq, has increasingly become a target for the Sunni Muslim militants.Prime Minister Ahmet Davutoglu blamed ISIS for the bombing on January 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 southeast 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.Another report adds: A Turkish security force campaign against Kurdish militants in the southeast has been largely completed, Prime Minister Ahmet Davutoglu was reported as saying on Tuesday, as he outlined plans to maintain tighter control in parts of the region.Police and military launched operations against Kurdistan Workers Party (PKK) fighters in towns across the mainly Kurdish region last month, after the conflict reignited with the collapse of a two-year-long ceasefire in July.The army says it killed more than 500 PKK rebels in the campaign, adding to a death toll of more than 40,000 people killed since the PKK took up arms in 1984. The pro-Kurdish HDP party says about 100 civilians have been killed in the fighting.