Turkey, Saudi Arabia and Pakistan will sign a ​joint defence agreement in Mecca on Friday, sources with knowledge of the matter said, amid regional turmoil with Gulf states coming under fire from Iran after it was attacked by the U.S. and Israel, Reuters reported. 

While the pact further cements a burgeoning grouping of major Sunni Muslim powers allied with the United States, there was no immediate clarity on each state's commitments or how it might affect the wider crisis in the Middle East.