ISLAMABAD: Hundreds of Pakistanis enraged at debilitating gas shortages set two armoured police vehicles alight and blocked the highway to Islamabad airport on Friday, witnesses said.

The crowd, who also pelted police with stones, gathered at the main highway connecting the international airport to the capital city and blocked it for several hours for the second time in a week.

“More than 300 people gathered on the highway and put two armoured vehicles of police and a shed on a bus stop on fire,” an AFP photographer said.

“Police used the tear gas to disperse the protestors,” he said.

The protestors had gathered on the same highway on Monday and set fire to tyres, threw stones at police and private vehicles over gas rationing that has left thousands of homes without heat for hours at a time.

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 police official said that the road remained closed for more than three hours.

“There were still some boys on the road but we have opened it for the traffic after majority of the protestors dispersed following the three hours blockade,” Mirvais Niaz Khan, a senior official of the traffic police told AFP.

“They burnt our two armoured vehicles, so tear gas was used to disperse them,” he said.

Another police official said that the traffic remained gridlocked hours after the road was cleared because hundreds of vehicles had backed up on roads in Islamabad and Rawalpindi, which connected to the capital by road links.

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.