HOMS - The Syrian city of Homs has been subjected to its most severe bombardment in five months, activists say.

Aircraft and artillery targeted the neighbourhood of Khaldiya, the Syrian Observatory for Human Rights said.

There are also reports of fresh violence across the country.

Activists reported fierce clashes in the second city Aleppo, and government shelling in the capital Damascus, Hama, and Idlib.

The fighting comes after the UN Security Council condemned a deadly Syrian mortar strike on a Turkish town.

"It seems like the regime has a limited window to use its warplanes, because it is throwing everything it can at the rebels in Homs," the head of the London-based Syrian Observatory for Human Rights, Rami Abdel Rahman, told AFP news agency.

Syrian government forces subjected Homs to months of intense bombardment until April, after which the focus of the violence shifted to other cities.

The Local Co-ordination Committees activist network reported anti-government demonstrations on Friday in a number of towns and cities including Damascus and Aleppo.

Meanwhile, rebel fighters said they had captured an air base with a stock of missiles outside the capital, Damascus.

Syrian rebels have increasingly targeted air bases as government forces have stepped up the use of air strikes.

According to activists, more than 30,000 people have been killed since the uprising against President Bashar al-Assad began in March last year. The UN estimates that at least 20,000 have died.

The Observatory put Thursday's death toll from fighting in Syria at 180.

On Thursday, the UN Security Council said the strike on the Turkish border town of Akcakale underscored the grave impact the Syrian crisis was having on "regional peace and stability". Two women and three children were killed.

An earlier UN draft referring to "international peace and security" was blocked by Syria's ally Russia.

Turkey's parliament authorised troops to launch cross-border operations against Syria for a period of one year.

However, Turkish Prime Minister Recep Tayyip Erdogan has said his country did not intend to start a war with Syria.

Russia has consistently blocked UN Security Council resolutions, saying it does not support regime change in Syria.

China - another veto-wielding UN power - has also sided with Russia.