|Troops have reportedly resumed attacks despite agreeing to pull out from urban areas under an Arab League plan
Security forces in Syria are said to have killed at least 15 civilians as anti-regime demonstrations were staged across the country on the first day of the Muslim feast marking the end of the Hajj.
It was the fourth straight day of deadly violence since Syria agreed to an Arab League peace blueprint aimed at ending nearly eight months of bloodshed.
Ten of the deaths reported on Sunday occurred in Homs, 140km north of the capital Damascus, where a main district has been under tank bombardment since Tuesday according to activists.
Two demonstrators were killed when security police fired at a protest demanding the removal of President Bashar al-Assad in Hama, the northern Syrian city, the Syrian Revolution General Commission (SRGC) said on Sunday.
Another three demonstrators were said to have been killed in Idlib, in the north-west of the country.
The SRGC said in a statement that at least 10 protesters were also injured in the town of Talbisah, near Homs, and in Harra, in the southern Hauran plain.
French Foreign Minister Alain Juppe said it was clear that Assad's regime had no intention of ending its bloody bid to crush dissent.
Sheikh Hamad bin Jassim,Qatar's prime minister, called for Arab states to meet next Saturday to discuss the Syrian government's failure to take steps to solve its crisis, Egypt's official news agency MENA reported.
The meeting would discuss "the continuing violence and the government's failure to stick to its obligations under the Arab Action Plan to solve the crisis in Syria," it said.
Troops 'surrounding mosques'
Fifty protesters were arrested after a demonstration in the Damascus district of Kfrar Souseh, according to the SRGC.
Troops deployed in several Damascus suburbs were surrounding mosques to prevent crowds from rallying after the early morning prayers for the Eid feast, it said.
Al Jazeera was unable to independently verify these reports.
Officials say the unrest is largely a result of a foreign conspiracy to divide Syria and that security forces are using legitimate means to confront "terrorists" and "Islamist militants" fighting against a reform drive by Assad.
"The failure of the Arab solution would lead to catastrophic results for the situation in Syria and the region as a whole"
- Nabil Elaraby,
Arab League secretary-general
Activists and residents said tank fire has killed at least 13 civilians and wounded dozens in Homs on Saturday, casting doubt on whether an Arab League plan can end the bloodshed triggered by the popular uprising.
"Whole buildings have been gutted by tank fire. Bread has run out and people who get hit in the streets are dying from their wounds on the spot because no one can reach them," Samer, a local activist, said.
The latest deaths brought the number of civilians reportedly killed in Homs to more than 80 since Tuesday.
In a live address to Syrians via Al Jazeera, Burhan Ghalioun, a prominent opposition figure, said the Syrian National Council, which was formed in the Turkish city of Istanbul two months ago, had asked the Arab League and UN to help protect the civilian population by sending in international human rights monitors.
"We'd not exclude any option ... and we will continue to garner international support. The regime aims to gain time from every initiative. It is wrongly betting on pushing the country into chaos and civil war," Ghalioun said.
Arab League warning
The head of the Arab League has said the organisation is seriously concerned by ongoing violence and appealed to Syria to abide by steps agreed this week with Arab states to protect civilians and set the country on the course of dialogue.
"The failure of the Arab solution would lead to catastrophic results for the situation in Syria and the region as a whole," Nabil Elaraby said in a statement from the Egyptian capital, Cairo, on Saturday.
To mark the Muslim feast of Eid al-Adha, Syria has freed 553 people arrested during anti-government protests while condemning the US for suggesting Syrians reject an amnesty offered to lay down their arms.
Al Jazeera's Nisreen El-Shamayleh, reporting from Amman, in neighbouring Jordan, said that many Syrians see the fresh violence as "a slap in the face of the Arab League".
"They do not believe in the Arab League peace initiative. Many activists say the organisation is 'impotent'."
The Syrian government blames "foreign-backed armed gangs" for the violence and says they have killed 1,100 members of the security forces since the uprising began in March against 41 years of rule by Assad's family and their Baath Party.
The UN says more than 3,000 people have been killed in the crackdown.
Arab leaders have increased criticism of Assad as the killings mounted, but are cautious about the notion of major political change in the country for fear this could cause chaos, given Syria's sectarian divisions.
Syria is dominated by Assad's minority Alawite sect while Sunni Muslims form the majority.
For the same reason, together with Syria's location along fault lines of Middle East conflict, Western countries have shown no inclination for a repeat of the NATO bombardment that was key in the fall of Libya's Muammar Gaddafi.
Assad has been strengthening an alliance with Iran, started by his late father, Hafez al-Assad, while continuing his policy of avoiding confrontation with Israel on the occupied Golan Heights frontier after a 1974 ceasefire.
In-depth coverage of escalating violence across Syria
The opposition has so far rejected talks with Assad as long as violence continues and has said the only way to restore peace is for the president to step down immediately.
"How can we talk about a dialogue when Syrians cannot meet each other, express an opinion or an ideology without being in danger? These rights have to be guaranteed for participation in public issues," Aref Dalila, a prominent dissident, said.
Dalila is an economist who was jailed for eight years after criticising a mobile phone concession that was awarded to a cousin of Assad.
State television announced on Friday amnesty to anyone with weapons if they reported to police within a week, "as long as they did not commit any crimes of killing".
The same day, security forces killed at least 20 people and wounded dozens across Syria, activists said. State television denied that any protesters were killed on Friday.
The amnesty did not appear to be part of the Arab League plan, accepted by Syria on Wednesday, under which the army would leave turbulent cities, political prisoners would go free and talks with the opposition would begin within two weeks.
Rights campaigners say tens of thousands of Syrians have been arrested since the start of the uprising, with thousands more counted as missing.