The 57-member Organisation of Islamic Cooperation has suspended Syria, with OIC chief Ekmeleddin Ihsanoglu saying early Thursday the move sent "a strong message" to Damascus.
A statement issued at the end of an OIC summit meeting in the Saudi holy city of Mecca said participants had agreed on "the need to end immediately the acts of violence in Syria and to suspend that country from the OIC."
The final statement said there had been "deep concern at the massacres and inhuman acts suffered by the Syrian people."
Ihsanoglu told a news conference the decision sent "a strong message from the Muslim world to the Syrian regime."
"This world can no longer accept a regime that massacres its people using planes, tanks and heavy artillery," he added.
It was "also a message to the international community stating that the Muslim world backs a peaceful solution (in Syria), wants an end to the bloodshed and refuses to let the problem degenerate into a religious conflict and spill over" into the wider region," Ihsanoglu said.
The emergency summit of the world's largest Islamic bloc opened late Tuesday with the suspension proposal put forward by a preparatory meeting of foreign ministers, a symbolic attempt to pile pressure on Damascus over its deadly crackdown on a 17-month uprising.
The move by the OIC, which represents 1.5 million Muslims worldwide, is aimed at further isolating Syrian President Bashar al-Assad's embattled regime, but its effect is seen as being largely symbolic.
Syria was suspended from the Arab League last year over its clampdown on the uprising that Assad characterised as a plot by Western and rival powers to overthrow his regime.
Saudi King Abdullah presided over the meeting, attended by Iranian President Mahmoud Ahmadinejad whose country has openly criticised the push to suspend Syria.
In a second statement called the "Mecca Pact," the participants proclaimed their support for "Muslim people who are oppressed like the Syrian people."
It underlined the summit's support for "the oppressed Muslim peoples... who face the combat aircraft and heavy guns of the regular armies as is the case of the Syrian people."
The statement backed cooperation between Muslim states, the fight against divisions between Muslims, promotion of "moderate" Islam and the "fight against terrorism and the thinking behind it."
It described as a "crime against humanity" the Myanmar government's handling of minority Muslims and reiterated support for the Palestinians.