Syria signed a protocol on Monday to allow in monitors, part of an Arab peace plan that aims to end a nine-month crackdown on protests against President Bashar Assad's rule.
A Reuters witness saw Syrian Deputy Foreign Minister Faisal Mekdad sign the protocol at the Arab League headquarters in Cairo and a League diplomat confirmed it had been inked.
Syria has stalled for weeks over signing the protocol on monitors, although it had agreed to other parts of the plan. The League suspended Syria from the pan-Arab body and announced sanctions against Damascus.
The initiative calls for withdrawing the army from towns, freeing thousands of political prisoners, starting dialogue with the opposition and letting monitors into the country.
A senior official at the Cairo-based League said the pan-Arab body had not been officially informed as of Monday morning that Damascus would sign the protocol.
Egypt's MENA news agency said the Syrian diplomat did not say who would sign the deal on Syria's behalf. Cairo airport sources said Syrian Deputy Foreign Minister Faisal Mekdad arrived in Cairo on Monday.
League chief Nabil Elaraby was due to hold a news conference at about 1 p.m. (1100 GMT), which officials said was to announce "important" news. They did not give details.
The Arab League has suspended Syria's membership and announced sanctions over Assad's refusal so far to sign the deal. Arab ministers are set to meet later this week and could decide to submit their plan to the UN Security Council, making it a potential basis for wider international action.
Meanwhile, Syrian human rights organizations reported that at least seven people were killed in the cities of Homs, Iblin, and Dir Azur on Monday morning.
On Sunday, mass protests against Assad's regime continued, resulting in the death of 24 people. A rare protest also took place in central Damascus, which was scattered by security forces.
Armed resistance has emerged in the last two months in Syria, alongside a peaceful protest movement that began in March inspired by uprisings across the Arab world.
Loyalist forces, including a pro-Assad militia, have reportedly taken scores of casualties from insurgents in the last few weeks, especially in the northwestern province of Idlib near Turkey and in the central region of Homs.
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