The Arab League approved economic sanctions on Syria on Sunday to try to force Damascus to halt an eight-month crackdown on protests against President Bashar al-Assad that Qatar said may prompt international intervention.
Anti-Assad activists said there was no respite from the crackdown and security forces had killed at least 24 civilians, many in a town north of Damascus that has become a focus for protests demanding Assad's removal. Others were killed in raids on towns in the province of Homs.
Nineteen of the League's 22 members approved the decision to immediately enforce the sanctions, hailed by Britain as unprecedented. They include a travel ban on top Syrian officials and a freeze on assets related to Assad's government.
"The indications are not positive ... the sanctions are still economic but if there is no movement on the part of Syria then we have a responsibility as human beings to stop the killings," Sheikh Hamad bin Jassim al-Thani, Qatar's prime minister and foreign minister, told reporters.
"Power is not worth anything when a ruler kills his people," he said, adding that the sanctions were also aimed at halting dealings with Syria's central bank and investment in Syria.
Sheikh Hamad said Arab nations wanted to avoid a repeat of what happened in Libya, where a U.N. Security Council resolution led to NATO air strikes. He warned other Arab states that the West could intervene if it felt the league was not "serious."
"All the work that we are doing is to avoid this interference," he said.
British Foreign Secretary William Hague said the "unprecedented decision to impose sanctions demonstrates that the regime's repeated failure to deliver on its promises will not be ignored and that those who perpetrate these appalling abuses will be held to account."
Hague said Britain hoped the move would help break what he called United Nations silence "on the ongoing brutality taking place in Syria" after Russia and China thwarted Western efforts to pass a U.N. Security Council resolution on Syria.
Damascus, where the Assad family has ruled for 41 years, says regional powers helped incite the violence, which it blames on armed groups targeting civilians and its security forces.
The president of the Union of Arab Banks, a division of the Arab League, expected the sanctions to hit Syria's central bank, which he said has "big deposits" in the region, especially the Gulf.
"Once individual countries that have voted for the sanctions issue instructions, Syrian deposits will be frozen, which will affect the financial resources of the Syrian government," Adnan Youssef told Arabiya television.
Arab ministers were spurred to action by worsening violence in Syria and by the Assad government's failure to meet a deadline to let in Arab monitors and take other steps to end its crackdown on the uprising.
"It is a symbolic but a huge step. The Arab League has tried to stop civilian killings but it failed. Now it is removing the Arab cover from the regime, which could make it easier for the international community to intervene," said opposition figure Walid al-Bunni.
"No one wants to see ordinary Syrians deprived of essential supplies. The Arabs are telling Bashar: 'You are killing the people to whom you say you belong. We will not receive you in our capitals. We're freezing your assets. We are not investing in your country,'" Bunni said from Cairo.
Even so, the measures could plunge Syria deeper into economic crisis. Syrian official media quoted an undated letter by Syrian Foreign Minister Walid al-Moualem to the Arab League as saying Damascus viewed the plan for monitors as interference in its affairs. "We trust that all Arab countries stand against foreign interference in the affairs of Arab countries. Therefore we hope that the League will issue (a statement) confirming this," he said.
The League for decades avoided action against its 22 members.
But it has been galvanised by pressure from Gulf Arabs, already angry at Syria's alliance with regional rival Iran, by the political changes brought about by Arab uprisings, and by the scale of the Syrian bloodshed.
Troops backed by armor killed 11 people, including two children, in Rankous, a town 30 km (19 miles) north of Damascus as they raided houses looking for activists who had taken part in anti-Assad rally on Friday that was broadcast live on al-Jazeera television, activists said.
"It is difficult to know what is happening in Rankous exactly. The communications have been cut. A couple of Facebook messages that trickled from there talked about heavy tank fire on the town," said one activist, who lives in Damascus and gave his name as Fares.
"There were hit-and-run attacks by insurgents on loyalist forced in Rankous last week. The raid today may be also in revenge of that," he said.
In the eastern city of Deir al-Zor, security police killed two people and wounded 10 at a funeral of an activist.
"The funeral came under fire at the mosque when the crowd started chanting 'the people weren't the downfall of the regime'," Abu Jassem, an activist in the city, said by phone.
In al-Ghab plain, northwest of the city of Hama, troops arrested dozens of villagers in the town of Kfar Nbouzeh, burned six houses belonging to activists and ransacked shops, the Syrian Observatory for Human Rights said, adding that 11 people were also killed in the central province of Homs.
"Even regular food stores were not spared from the ransacking," said Rami Abdelrahman, the Observatory's director.
The United Nations says the crackdown has killed more than 3,500 people. Along with peaceful protests, some of Assad's opponents are fighting back. Army defectors have loosely grouped under the Syrian Free Army and more insurgent attacks on loyalist troops have been reported in the last several weeks.
The defectors are drawn from the majority Sunni rank and file. The military and security apparatus are dominated by officers from Assad's minority Alawite sect, an offshoot of Islam that has controlled the majority Sunni country for the last five decades.
Hundreds of people, including civilians, soldiers and army deserters, have been killed in Syria this month, possibly the bloodiest since the unrest broke out in March inspired by uprisings which overthrew leaders in Tunisia, Egypt and Libya.
Alongside the mainly peaceful protests, armed insurgents have increasingly attacked military targets in recent weeks. Officials say 1,100 security force members have been killed.
(Additional reporting by Dominic Evans in Beirut, Patrick Werr and Tom Pfeiffer in Cairo, and Patrick Markey in Baghdad; Writing by Khaled Yacoub Oweis; Editing by Ruth Pitchford)