BEIRUT (AFP) - People wounded in fighting between rebels and regime troops in the central Syria city of Homs are dying for lack of medical equipment, a watchdog said on Tuesday.

"The army's continuous bombardment over the past 11 days has made the critical humanitarian situation in rebel areas of Homs even worse," Syrian Observatory for Human Rights director Rami Abdel Rahman said.

"An unknown number of rebels and civilians wounded in recent days are dying from their injuries, because there is no medical equipment to treat them," he added.

Khaldiyeh and the Old City neighbourhoods of Homs have been under tight army siege for more than a year and since late June have come under steady shell and rocket fire as well as air strikes in a withering offensive by the regime.

"The little medical equipment the rebels could get into these areas was coming through underground tunnels. Now, these have been bombed too," Abdel Rahman said.

Activists on the ground confirmed the shortage of medical care.

"The medical community in the besieged areas of Homs is suffering from shortages," said Homs-based activist Yazan.

Large quantities of medical supplies, Yazan said, had been used up due to the increased number of injuries caused by the shelling.

"This campaign on Homs has been the fiercest" since the start of the siege on the city's rebel areas more than a year ago, he added.

Witnesses and activists have said Syria's forces have been joined in the assault aimed at driving rebels out of the centre of the city by fighters from the Lebanese Shiite movement Hezbollah.

At the start of the revolt against President Bashar al-Assad in March 2011, Homs was dubbed "the capital of the revolution" when it was shaken by widespread protests calling for regime change.

Now, the rebels are caught in a small segment of the city, barely covering some two sq km in the centre.

Early Tuesday, the army shelled the rebel zones as fresh fighting erupted in the streets, said the Observatory.

The UN has said more than 2,500 civilians are trapped in Homs' besieged areas.

More than 100,000 people have been killed in Syria's 27-month war, most of them civilians, says the group.