Gunmen on motorbikes in southwestern Pakistan on Monday set ablaze at least 19 oil tankers carrying fuel for US-led NATO forces in neighbouring Afghanistan, officials said.

The gunmen fired at the tankers as they were waiting for a police escort on the main highway at Kolpur village, 25 kilometres (15 miles) south of Quetta, the capital of restive Baluchistan province, police official Ismail Kurd said.

"Thirteen oil tankers were completely burnt, while six were partially damaged and seven others remained safe," Kurd told AFP, adding that there were no casualties.

"There were about a dozen gunmen who came on motorbikes, fired at oil tankers and when the fire started they fled," he said.

Provincial home secretary Zafarullah Baloch confirmed the attack.

There was no immediate claim of responsibility but Taliban militants have carried out similar attacks in the past to disrupt supplies to US-led troops fighting against the militia in Afghanistan for the past 10 years.

The United States ships the bulk of its supplies and equipment for Afghanistan through Pakistan, but is increasingly sourcing alternative routes.

According to The Washington Post, the United States moved 90 percent of its military surface cargo in 2009 through the Pakistani port of Karachi and then through mountain passes into Afghanistan.

But now almost 40 percent of surface cargo arrives in Afghanistan from the north, along a patchwork of Central Asian rail and road routes that the Pentagon calls the Northern Distribution Network, the paper said.