(CNN) -- The Organization of Islamic Cooperation suspended Syria Wednesday from membership.
"There is a strong concern over the massacres and the inhumane acts that are being committed against the Syrian people," said Nizar bin Obaid Madani, Saudi Arabia's state minister for foreign affairs.
"Therefore, the leaders agreed on the importance of preserving the unity of Syria, the immediate end of all acts of violence and the suspension of Syrian membership within OIC," the minister said after a two-day summit of OIC heads of state.
Iran and Algeria were the sole opponents in the 57-nation body, which represents 1.5 billion Muslims.
The organization's move sends a message to Syrian President Bashar al-Assad that its members will not accept the regime killing its people, OIC Secretary-General Ekmeleddin Ihsanoglu told CNN.
He also called on the U.N. Security Council to approve tougher resolutions against the regime.
Asked if OIC members supported military intervention, Ihsanoglu said he heard few such calls.
U.S. State Department spokeswoman Victoria Nuland commended the move. "Today's action underscores the Assad regime's increasing international isolation and the widespread support for the Syrian people and their struggle for a democratic state that represents their aspirations and respects their human rights," she said in a statement.
The development came as would-be rescuers searched for survivors amid the rubble left after Syrian government forces shelled a town in Aleppo province near the border with Turkey, killing 40 people, a spokesman for the rebel Syrian National Council told CNN.
"We have no special equipment to search or lift the wreckage," said the spokesman, Abu Omar, by Skype from the province. "People are doing it using their bare hands and rudimentary tools."
Another 40 people in the town of Azzaz were missing after the shelling, which targeted a popular food market, Omar said.
Among the dead were four Lebanese hostages who had been taken by an armed group called "the revolutionaries of Aleppo" that is not affiliated with the Free Syrian Army, he said.
He described the victims as civilians, including women and children, and said the town was without electricity.
The attack came after government had warned members of the al-Tawheed Brigade, the main rebel group fighting in the city of Aleppo, to pull its fighters out of the city or face shelling from warplanes, Omar said.
Inside Aleppo, Syria's largest city, the rebels "continued clashes today with the regime forces in Salaheddine district" and Bab el-Nasr neighborhood, killing a rebel commander, he added.
Meanwhile, a United Nations commission concluded Wednesday that both Syrian regime forces and anti-government rebels have committed war crimes in the Syrian conflict.
The U.N. Independent International Commission of Inquiry said government forces and their Shabiha militia allies committed crimes against humanity such as "murder and torture, war crimes and gross violations of international human rights and humanitarian law, including unlawful killing, indiscriminate attacks against civilian populations and acts of sexual violence."
In the town of Houla on May 25, the commission said, al-Assad's forces and militia allies were responsible for killing more than 100 civilians, nearly half of them children.
The anti-government armed groups that have emerged over the past year also have committed war crimes, including "murder, extrajudicial killings and torture," the report says. But the commission says these actions "were not of the same gravity, frequency and scale as the ones perpetrated by government forces and the militia."
Since February 15, the report says, "the situation in the country has deteriorated significantly with armed violence spreading to new areas and active hostilities raging between rebels and the government and the militias."
The violence continued Wednesday, with at least 205 people killed, the opposition Local Coordination Committees of Syria said. Ninety of them were in Aleppo province, and most of them were in Azzaz, a town near the Turkish border that was shelled by regime warplanes.
Opposition activists have put the death toll in the 17-month crisis at more than 20,000.
CNN's Arwa Damon in Beirut, Amir Ahmed and Holly Yan in Atlanta, Ben Wedeman in Aleppo, Nic Robertson in Jeddah contributed to this report.