Pressure mounted on the Damascus regime, with the top UN human rights official saying that crimes against humanity have probably been committed in the bloody crackdown on dissidents since March last year.
"The nature and scale of abuses committed by Syrian forces indicate that crimes against humanity are likely to have been committed since March 2011," High Commissioner for Human Rights Navi Pillay told the UN General Assembly.
The Arab League agreed yesterday to ask the United Nations to send a joint peacekeeping force to Syria, where activists say more than 6,000 people have died in the crackdown.
President Bashar al-Assad's regime swiftly rejected the initiative.
Hours after the League's decision, Assad's troops resumed shelling Baba Amr, a rebel bastion in the central city of Homs, the Syrian Observatory for Human Rights said.
"The neighbourhood of Baba Amr has been subjected to sporadic shelling since 5:00 am (local time) by the Syrian army," the Britain-based group said in a statement.
Regime forces killed eight civilians, among them three in Homs and two in nearby Rastan, including a 13-year-old girl in shelling after clashes between army defectors and soldiers. Three troops also died.
Security forces also raided homes to arrest people in the southern Daraa province, cradle of the Arab Spring-inspired 11-month uprising against Assad's iron-fisted rule.
"There were fierce clashes between defectors and the army which stormed Lajat (also in Daraa province) and arrested the mothers of four dissidents," the Observatory said.
Despite the relentless violence, protests were staged across Syria.
Some denounced Assad and others supported the rebel Free Syrian Army, according to YouTube videos provided by the Local Coordination Committees, an activist network.
"Arab League!!! Thank you but we need more," said a placard students carried at a rally in Jabala, Idlib province.
A government official said Syria was determined to crush such dissent, regardless of the latest Arab initiative, the official SANA news agency reported.
"This decision will not prevent the Syrian government from fulfilling its responsibilities in protecting its citizens and restoring security and stability," the unidentified official was quoted as saying.
"Syria rejects decisions that are a flagrant interference in the country's internal affairs and a violation of its national sovereignty."
Activists say Assad's forces have killed at least 500 people in Homs since they began bombarding it on February 4 --the same day Russia and China vetoed a second UN Security Council resolution on Syria.
That move prompted the pan-Arab bloc to ask for a joint Arab-UN peacekeeping mission.
"The risk of a humanitarian crisis throughout Syria is rising," warned Pillay in her UN address.
"The failure of the Security Council to agree on firm collective action appears to have emboldened the Syrian government to launch an all-out assault in an effort to crush dissent with overwhelming force."
The Arab initiative was welcomed by Russia, the European Union and other Western powers.
EU foreign policy chief Catherine Ashton said the Arab League had taken "significant decisions to increase the international pressure on the Syrian regime" and urged the Security Council to act in order to stop the violence.