Arab League Chief Nabil al-Arabi on Sunday called on Syrian authorities to "immediately halt" a violent crackdown on anti-government protests and expedite steps to preserve the country's unity.

"The chance is still available for fulfilling the reforms, which President Bashar Assad promised to respond to the Syrian people's ambitions and legal demands for freedom and change," added al-Arabi in a statement.

He made the remarks as the Syrian army was continuing attacks against two restive cities, resulting in at least 60 deaths, according to opposition activists.

Al-Arabi also called on the Syrian government to set up an independent team to investigate violence and human rights abuses in the country.

"The Syrian government and national powers should take all necessary steps to provide a favorable climate for serious engagement in a comprehensive national dialogue," added al-Arabi.

He warned against what he termed as risks of sliding into sectarian sedition and chaos in Syria.

During a visit to Damascus last month, al-Arabi criticized foreign "interference" in Syrian affairs.

At least 60 Syrian civilians were killed in armored military assaults by President Bashar Assad's forces on Sunday to crush a five-month uprising against his rule, a grassroots activists' organization said.

Among them were 38 in the eastern city of Deir al-Zor and 13 in the Houla Plain, 30 km (19 miles) north of the city of Homs, which were stormed by tanks and armored vehicles early on Sunday, the Syrian Revolution Coordinating Union said.

"These are preliminary figures. The numbers of casualties are escalating by the hour," activist Suhair al-Atassi, a SRCU member, told Reuters by phone from Damascus.