Syria's membership has not been fully suspended, Al Jazeera said, but Syrian delegates will no longer be allowed to participate in the regional body's meetings.
The League also called for economic and political sanctions and talks with the Syrian opposition, Al Ahram reported. Members may withdraw their ambassadors from Damascus.
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The decision was taken at an emergency meeting in Cairo, Egypt, on Saturday.
A total of 18 member countries agreed to it, while Lebanon, Yemen and Syria opposed it, the Associated Press reported. Iraq abstained from the vote.
The suspension will take effect from Wednesday onward, said Qatar's Prime Minister Hamad Bin Jassim, cited by Reuters. It will last until Syria implements a plan to end the bloodshed.
The Arab League may also seek assistance from the wider international community, Jassim said:
"If the violence and killing doesn't stop, the Secretary General will call on international organizations dealing with human rights, including the United Nations."
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The Arab League is unwilling to expel Syria, one diplomat told Al Ahram ahead of Saturday's meeting:
"There are not enough countries who are convinced that it is a good idea to freeze Syria's membership in the Arab organisation, and those who oppose are about eight countries [of the 22 member states] who are convinced that if you isolate Damascus you are antagonising the regime, rather than encouraging it to end the violence."
Syria's Arab League delegate Youssef el-Ahmed, cited by Reuters, condemned the suspension and accused the Arab League of "serving a Western and American agenda."
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Syrian security forces have continued to use violence against protestors, despite an Arab League-brokered peace deal that was supposed to see soldiers withdrawn from the streets and prisoners released from jails.
Torture and unlawful killings continue in the central city of Homs, according to a Human Rights Watch report published this week.
More than 3,500 people have died in the anti-government protests since March, the UN said Tuesday.
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