Taliban sources tell The Daily Beast that the Afghan insurgents now have a new, far more devastating explosive for attacks on U.S. and NATO facilities in Afghanistan. Today’s massive Taliban truck-bomb explosion at a military base in Paktia province appears to have been only the latest such attack. “The new explosive is so destructive and powerful that the leadership council has been advised to prevent civilian casualties by ordering the evacuation of all homes within 15 kilometers [roughly 10 miles] of U.S. and NATO bases,” says a well-placed source in the Taliban’s military council for southern Afghanistan. The decision was taken at a meeting about a month ago, he says.

Speaking to The Daily Beast not far from the Pakistani-Afghan border, the council member said the insurgents have used the explosives in other recent bombings. One such attack was the suicide bombing this past June in Khost province at the gates of Camp Salerno, America’s third-largest base in Afghanistan, where two U.S. service members reportedly died. Another was the insurgents’ high-profile September assault in Helmand province at Camp Bastion, where Britain’s Prince Harry is stationed as a helicopter pilot. Two U.S. Marines were killed, and millions of dollars worth of aircraft and other equipment were destroyed.

A Taliban intelligence official declines to say just where the insurgents are getting the new explosives, but he contends that everyone in the region is opposed to a permanent U.S. military presence in Afghanistan. “The primary aim of the attacks is to send a message to the Americans that remaining in their bases after 2014 won’t be an easy deal,” says the council member.

It’s not a pretty picture, says an Afghan government intelligence official. “We know the Taliban are using new munitions against Afghan and NATO bases,” he says. “The reason is clear: Pakistan is warning the U.S. and Afghan governments not to let the Americans remain in Afghanistan. The attacks on U.S. camps in Khost and Helmand—and today in Paktia—are clear messages from Pakistan and perhaps even Iran as well. Pakistan wants to push a new phase of the insurgency with attacks on big bases to undermine U.S.-Afghan ties after 2014.”

The Taliban’s recent moves have made it hard for the Afghan government’s uniformed forces to think so far into the future. A few years ago, military patrols used to find caches of only 20 or 30 kgs of explosives, says an Afghan security officer and explosive expert in the southern city of Kandahar. “Nowadays,” he says, “each cache is between 50 and 500 kgs. It worries us. We’ve caught trucks loaded with as much as 1,000 kgs.”

Military bases are built in such a way that only the outer gates can be damaged by an initial blast, the security officer says. Nevertheless, he says, the stuff the insurgents are using now is so powerful that a bomb can cause real damage inside a base even if the blast is set off well outside the gates. “Some of what we see is small in quantity but huge in quality,” he says. “We’re pretty sure it’s not homemade.” In fact, he says, it appears to be coming from military ordnance factories in neighboring Pakistan and maybe Iran—and the supply seems to be unlimited.