The Arab League demanded on Thursday that Russia stop supplying arms to Syria, as a regime onslaught of Homs and its surrounds appeared to stall a Red Cross bid to rescue trapped civilians.

The pan-Arab bloc's deputy secretary general Ahmed Ben Hilli issued the appeal in an interview in which he also called for UN-Arab League envoy Kofi Annan's mandate to be revamped, and for Iran's inclusion in talks on Syria.

"Any assistance to violence must be ceased because when you supply military equipment, you help kill people. This must stop," Hilli was quoted as telling Interfax news agency in comments translated into Russian.

"To make (the Annan) plan work, we need to find a new mechanism and the mandate of the special envoy must be reassessed, so we can be sure that all the sides are observing the plan," he said without elaborating.

He backed Iran joining the Syria Contact Group meeting expected to be held in Geneva on June 30, while saying that Tehran's participation was still at the discussion stage.

"In my view, all the players taking part in the Syrian crisis must be part of this contact group," he was quoted as saying in answer to a question about Iran's participation.

"The main task at the moment is agreeing the agenda of the first meeting. Then a decision will be taken on who will take part in this conference," he added.

Russia has steadfastly resisted Western pleas to help remove Syria's President Bashar al-Assad from power despite the escalating hostilities that have battered Annan's UN-backed peace initiative.

"We believe that nobody has the right to decide for other nations who should be in power and who should not," Russian President Vladimir Putin said on Tuesday after a G20 summit in Mexico.

On the ground, a torrent of heavy mortar and machinegun fire killed at least four people in and around Homs, the Syrian Observatory for Human Rights reported, a day after nearly 100 people died across the country.

Streaming video from Homs on the website showed smoke billowing from a residential district as the staccato of automatic gunfire was punctuated by the thud of mortar blasts.

At least two civilians were killed in Homs city, the Observatory's Rami Abdel Rahman told AFP.

The army also battered Qusayr, a town just southwest of Homs, after suffering heavy losses at the hands of anti-regime rebel fighters, a watchdog and a journalist said.

Qusayr, a rebel stronghold in Homs province, was surrounded by forces loyal to Assad who bombarded the town heavily, as helicopters hovered overhead, the journalist in the area said.

The shelling erupted at 7:00 am (0400 GMT), and was followed by fierce clashes with rebel forces concentrated near the town's main hospital.

Abdel Rahman said two unidentified people were killed as regime forces attacked Qusayr, which is situated near the border with Lebanon, with heavy machinegun fire and shelling.

Elsewhere, eight soldiers and a rebel were killed in heavy fighting at Arman az, in the northwestern province of Idlib, following a rebel attack on an army barracks, said the Britain-based group.

In the southern province of Daraa, cradle of a 15-month uprising against the Assad regime, the town of Inkhel was shelled and stormed by troops who then carried out a series of raids.

At least nine people were killed in Inkhel with the death toll likely to rise, said the Observatory.

The fresh bloodshed comes a day after violence cost the lives of 98 people across Syria, including 53 civilians, 35 soldiers and 10 rebel fighters, according to the Britain-based watchdog.

It appears to have halted a planned evacuation of hundreds of stranded civilians from the Homs area by the International Committee of the Red Cross.

The ICRC said on Wednesday that it had made a request for a temporary halt in fighting on Tuesday to the government and opposition groups. Both parties said they would respect the pause.

"Our first priority, together with the Syrian Arab Red Crescent, is to evacuate the wounded and the sick to safer areas, where they can be treated," said the ICRC's Beatrice Megevand-Roggo.

The Red Cross and the Red Crescent had been ready to enter Homs city, including the hard-hit districts of Khaldiyeh and Jourat al-Shiah, which activists say have been pounded mercilessly for days.

"The shelling is practically constant, and we can't get anybody out of the besieged districts," Abu Bilal, an opposition activist in the Homs area, told AFP via Skype on Wednesday.

"Electricity has been cut off for four days" in the Old City of Homs and "there's no more flour to bake bread. There really is nothing to eat," he added.

Last week the Observatory said more than 1,000 families were stuck in the region around Homs and spoke of dozens of people wounded in urgent need of medical care.