The Arab League on Sunday called on the Syrian authorities to "immediately" stop the violence that has rocked the country since mid-March, in the pan-Arab body's first official statement on the unrest.

League Secretary General Nabil al-Arabi "calls on the Syrian authorities to bring an end immediately to acts of violence and campaigns by the security forces against civilians," the statement said.

Syrian forces backed by tanks killed at least 57 people on Sunday in the regions of Deir Ezzor, Homs and Idlib, activists said, as President Bashar al-Assad defended what he termed the state's duty to crack down on "outlaws" despite mounting condemnation.

Security forces killed at least 38 civilians in the city of Deir Ezzor alone, activists said, and at least seven more died in Hula, a town in Homs province, in a separate assault with tanks.

Syria’s foreign ministry on Sunday rejected criticism from the Gulf Cooperation Council of Damascus’ violent crackdown on protests and called for Gulf states to instead condemn "the violence of armed groups” and to “allow time for the reforms" proposed by President Bashar al-Assad.

“Syria has received with regret the statement of the Gulf Cooperation Council (GCC), which completely ignored the information and facts presented by Syria on the killing and sabotage acts committed by armed terrorist groups seeking to undermine the homeland's sovereignty and security,” Syria’s state-run news agency SANA quoted a Syrian official source as saying.

Foreign Minister Adnan Mansour stressed on Sunday Lebanon’s rejection of all attempts to meddle in Syria’s internal affairs.

He said after holding talks in Damascus with Syrian President Bashar Assad: “Lebanon’s stability is linked to Syria’s stability.”

Syrian President Bashar Assad’s advisor Buthaina Shaaban criticized on Sunday’s Turkey’s position on the developments in Syria, saying that its Foreign Minister Ahmet Davutoglu will hear “stronger statements when he visits Syria.”

She said in a statement: “If the Turkish foreign minister believes that he is arriving in Syria to deliver a firm message, then he will hear a firmer message from us.”

Turkish Foreign Minister Ahmet Davutoglu will visit Syria on Tuesday with the message that Ankara "has run out of patience" with the ongoing violence, Prime Minister Recep Tayyip Erdogan said.

"We have reached the end of our patience and that's why I am sending the foreign minister to Syria on Tuesday," Erdogan was quoted by the Anatolia news agency as saying.

U.N. leader Ban Ki-moon told Syrian President Bashar Assad on Saturday to immediately end his deadly military campaign against opponents, the United Nations said.

Ban also said the use of mass arrests must also be halted in Syria in the first contacts between the two since April.

Security forces on Saturday arrested prominent opposition figure and former political prisoner Walid al-Bunni and his two sons, Syrian Observatory for Human Rights chief Rami Abdel Rahman said.

The arrests came after Syria vowed on Saturday to hold "free and transparent" elections by the end of 2011 as Arab states in the Gulf joined a chorus of Western pressure over its deadly suppression of anti-regime protests.

Foreign Minister Walid Muallem said on Saturday that elections to a new parliament will be held by year's end, as Syria's regime faces international pressure over its deadly crackdown on protests.

"Syria will hold free and transparent elections that will give birth to a parliament representing the aspirations of the Syrian people," Muallem said in a meeting with foreign ambassadors posted to Damascus.

United Nations High Commissioner for Refugees (UNHCR) committee said that Iran and Hizbullah are involved in killing Syrian soldiers who refused to shoot at anti-regime protesters, the French radio station reported on Saturday.

The committee reported that it will publish a detailed report from 20 pages during the upcoming days.