ISTANBUL — A two-day summit bringing together leaders of the Islamic world concluded in the Turkish city of Istanbul with a pledge to combat terrorism and overcome sectarian divide.

The final declaration Friday expressed strong condemnation of the Islamic State group and the role of Iran and its proxies in regional conflicts.

Turkish President Recep Tayyip Erdogan, who chaired the final session of the Organization of the Islamic Cooperation summit, lamented the fact that Muslim countries who are "the heirs of a civilization that was built on columns of peace and justice are being remembered more for wars, armed conflict, sectarianism and terrorism."

"As Muslims, we cannot overcome our difficulties without achieving unity in spite of our differences," said the Turkish leader during the closing ceremony after delegates took a break to perform Friday prayers.

Erdogan also said the establishment of an international arbitration body in Istanbul is part of the OIC 2025 action plan and welcomed a decision reached a day earlier to create a Turkey-based police coordination center aimed at increasing cooperation against terrorism.

The Istanbul meeting drew representatives from across the Muslim world, including King Salman of Saudi Arabia and Iranian President Hassan Rouhani, whose countries have squared off in Yemen and Syria.

The final declaration expressed hope that negotiations that started in Geneva on April 13 would contribute to resolving "the Syrian crisis as soon as possible" and "deplored Iran's interference" and "continued support for terrorism" not only in Syria but also Bahrain, Yemen, and Somalia.

At the sidelines of the summit, regional Sunni powers Turkey and Saudi Arabia signed a memorandum to create a bilateral cooperation council. The two countries are aligned in their support for rebel factions opposed to the government of Syrian President Bashar Assad.

The president of predominantly Shiite Iran, which along with Russia supports Assad, met Turkish Prime Minister Ahmet Davutoglu in Ankara on Friday after the summit. Rouhani is expected to meet with the Turkish president on Saturday.

Delegates at the conference pledged to combat terrorism in all its forms and condemned IS for its use of chemical weapons in Iraq. Turkey, which is facing renewed conflict with Kurdish militants in the southeast, underscored the threat posed by the Kurdistan Workers' party, or PKK, and its allies in Syria.

A PKK bomb attack in the southeastern Mardin province on Friday killed four members of Turkish security forces, according to Turkey's state-run Anadolu Agency. Turkey has endured a series of bombings since last summer, some claimed by Kurdish militants and others blamed by the authorities on IS.