ALEPPO, Syria - The Syrian army pressed its assault on rebels in commercial capital Aleppo on Sunday, while both sides reported atrocities and Arab foreign ministers postponed a planned meeting on the 17-month conflict.

The exiled opposition said pro-government militia had executed 10 civilians in a roundup in the flashpoint central city of Homs, while the official SANA news agency reported the murder of one of its staff, in the latest case of a pro-government journalist being killed.

The Arab League gave no reason for the indefinite postponement of its planned meeting in Saudi Arabia that had been due to discuss a replacement for international envoy Kofi Annan who announced his resignation earlier this month.

On Tuesday, Saudi Arabia is to host an Islamic summit focused on Syria to drum up support for the anti-regime revolt. Arab foreign ministers of the Gulf held talks late Sunday in the Saudi city of Jeddah to prepare for the summit.

In Aleppo, troops shelled rebel-held districts as fighting flared anew around a southwestern neighbourhood that rebel fighters had quit last week, the Syrian Observatory for Human Rights said.

The Shaar, Tariq al-Bab, Sakhur, Hanano and Bustan al-Qasr neighbourhoods all came under bombardment, as the army pressed a ground offensive it launched on Wednesday to recapture areas seized by rebels since July 20, the group said.

The Britain-based monitoring group also said that "communications of all forms have been cut off in the city of Aleppo as well as large areas of the province since the morning."

In the city of Homs, three children on a minibus were killed as they tried to flee with their parents from the Shamas district, where a military operation took place, it said.

The Observatory said 150 people were killed across the country on Sunday, including 49 civilians, 56 rebels and 45 regular soldiers.

In Damascus, gunfire was reported in the Qadam neighbourhood. Outside the capital, machinegun fire was heard in the town of Al-Tal, where 15 civilians were killed in shelling and clashes the previous day.

They were among 148 people -- 85 civilians, 43 soldiers and 20 rebels -- killed across Syria on Saturday, according to the Observatory.

On the situation in the capital, the pro-government Al-Watan newspaper spoke of "foiled bids to break the calm in Damascus, which was cleansed of terrorist groups who terrified residents."

In Aleppo, the paper said that the army was poised to assault the Sukari neighbourhood in the south of the city, after its recapture of the nearby Salaheddin district on Thursday.

Activist groups said 10 civilians were executed in a roundup of military-aged men in the Shamas district of Homs.

"Militiamen detained nearly 350 people from the Shamas district, assembled them in a courtyard and executed 10 of them," activist group, the Syrian Revolution General Council, said.

"The fate of the nearly 340 others is unknown and we fear greatly that they have met the same fate as the 10 martyrs," the group added.

State media targeted

The official SANA news agency said the head of its home news department, Abbas Ali, was assassinated by an "armed terrorist group" at his home in Jdaidet Artuz outside the capital on Saturday evening.

On Friday, rebels abducted three state television journalists as they accompanied government troops operating near Damascus, the Syrian Observatory said.

It came after a bomb attack on state television headquarters wounded several people last week and after an Al-Qaeda linked group claimed the abduction and murder earlier this month of state television presenter Mohammed al-Saeed.

As speculation mounted over who will succeed Annan when he steps down as international envoy later this month, UN chief Ban Ki-moon called for a "flexible UN presence in Syria" even after the mandate of the troubled observer mission he set up expires.

"A continued UN presence in Syria that goes beyond our important humanitarian work would allow systematic and meaningful engagement with the Syrian stakeholders, inside the country," the UN chief said.

The observer mission mandate is set to expire on August 19, after the Security Council voted last month to extend it for a "final" 30 days.

The mission -- originally 300 military observers and now reduced by half -- was deployed in April to oversee a peace plan, which should have begun with a ceasefire that never took hold.

In mid-June, the observers suspended patrols as fighting intensified.

The Security Council is scheduled to debate the future of the UN mission on Thursday, but so far there is little consensus on the conflict which the Observatory says has cost more than 21,000 lives since it began 17 months ago.

Diplomats in New York say veteran Algerian diplomat Lakhdar Brahimi, a former top Arab League official, has been tipped to replace Annan.

In the desert of northern Jordan, French military medics started on Sunday to set up a field hospital at the neighbouring country's main camp for Syrian refugees, outside the city of Mafraq.

Jordan is hosting more than 150,000 Syrian refugees.