Leaders from more than 50 Muslim nations accused Iran on Friday of supporting terrorism and interfering in the affairs of regional states, including Syria and Yemen, a condemnation that may widen the divide between Iran and its main rival, Saudi Arabia.

The leaders, including Iranian President Hassan Rouhani, have been attending a summit in Istanbul this week of the 57-member Organisation of Islamic Cooperation (OIC) to discuss such issues as the humanitarian fall-out from Syria’s civil war.

“The conference deplored Iran’s interference in the internal affairs of the States of the region and other member states including Bahrain, Yemen, Syria, and Somalia, and its continued support for terrorism,” the OIC said in its final summit communique.

It also stressed the need for “cooperative relations” between Iran and other Muslim countries, including refraining from the use or threat of force.

Both Turkey, which has assumed the three-year rotating presidency of the OIC, and Saudi Arabia are part of the US-led coalition against ISIL militants in Syria. They are also opponents of Syrian President Bashar Al Assad, a stance that has put them at odds with Iran, an ally of Assad.

Shi’ite Iran is also allied with the Houthi movement in Yemen, which has been battling forces loyal to Yemen’s Saudi-backed president in a conflict that has killed more than 6,000 people since March 2015.

While Turkey and Iran have stark differences over Syria, they have managed to keep their diplomatic and trade relations. Still, majority-Sunni Turkey is close to Saudi Arabia, which has cut diplomatic ties with Iran, and it is concerned about Tehran’s growing clout in Lebanon, Syria and Yemen.

A day before the communique, Iran’s Rouhani urged summit delegates to avoid sending out divisive messages.

“No message which would fuel division in the Islamic community should come out of the conference,” said Rouhani, according to Iranian state television.

In a speech at the summit’s closing news conference, Turkish President Tayyip Erdogan addressed the need to reconcile the divisions.

“We are Muslims, we will not allow Islam to be divided,” he said.

The leaders also condemned what they called the aggression of Armenia against Azerbaijan and called for the unconditional withdrawal of Armenian armed forces from the Nagorno-Karabakh region.

On Thursday, Erdogan said the countries had agreed to work more closely to fight terrorism and would establish an Istanbul-based centre for greater police cooperation.