Activists said on Saturday that Syrian forces' jets and mortars had pounded rebel-held areas of the city with "unprecedented" shelling.

"This is the worst campaign against the city since the revolution began," said an activist in the rebel-held old quarter of the city via Skype. "They are using all types of weapons," said the man on condition of anonymity for fear of government reprisals.

President Bashar al-Assad's forces want to gain control over the axis connecting Damascus to the Mediterranean.

The Britain-based Syrian Observatory for Human Rights said the all-out shelling was hitting the neighborhoods of Khaldiyeh, Bab Hub, Hamidiyeh and Bustan al-Diwan.

Syrian state media said the army was "achieving great progress" in Khaldiyeh. Saturday's bombardment on Homs follows steady military gains by Assad's forces in recent weeks, gains that have been credited somewhat to Syria being backed by Lebanese Hezbollah militants.

Foreign help

Three weeks ago, for example, Hezbollah assisted Assad's recapturing of the border town of Qusair, a former rebel bridgehead for smuggling guns and fighters. The rebels lost another town last week, called Tel Kalakh.

The recent moves by Assad's troops have alarmed international supporters of the rebels, leading the United States, for example, to announce that it will step up military support.

Hopes for a US- and Russian-backed peace conference have dimmed. Now that rebels are on the defensive militarily, they are reluctant to come to the negotiation table.

Yet, in spite of the lost ground around Damascus and Homs, rebels enjoyed a symbolic victory on Friday when they overran a major military checkpoint in Deraa, the southern city where the uprising first got under way.

tm/ccp (AP, AFP, Reuters)