ISLAMABAD: Hundreds of furious protesters blocked off the capital's airport highway on Monday, demonstrating against debilitating gas shortages and pelting police with stones, witnesses said.

A second angry crowd torched tyres in Islamabad and twin city Rawalpindi, throwing stones at police and private vehicles over gas rationing that has left thousands of homes without heat for hours at a time, an AFP reporter said.

Yawning energy shortfalls frequently trigger violent protests across Pakistan, where opposition parties are setting in motion campaigns designed to force elections earlier than scheduled in February 2013.

A mob blocked the main airport highway, forcing airline passengers to get out of their cars and walk with their luggage, and others to abandon their vehicles and walk home.

Thick black smoke spewed into the air from burning tyres, while protesters used stones and tree branches to shut down the road, an AFP reporter said.

A police official said protesters chanted slogans against the government and demanded an end to the gas shortages.

“The protesters are still on the road, even after police tried to disperse them. They are protesting against gas shortages for up to two kilometres (one mile),” said Ghulab Khan, an official in the police control room.

Separately traffic in Faizabad square, which links Islamabad to Rawalpindi, the headquarters of the Pakistan army, was blocked for more than five hours by several hundred protesters armed with sticks.

Pakistan, with a population of 174 million, produces only 80 per cent of its electricity needs, starving industry that has slumped in the face of recession and years of al Qaeda and Taliban-linked bombings.