A US drone fired two missiles on a militant compound in Pakistan's tribal North Waziristan region Friday, killing five Islamist fighters, security officials said.

Two missiles hit a house in Charkhel village west of Miranshah, the main town of North Waziristan, they said.

The strike is the latest in a series of US operations in the region which are believed to have targeted Taliban and Al-Qaeda extremists plotting attacks on Europe.

One security official in Peshawar told AFP: "At least five militants were killed in this US drone attack. The drone fired two missiles."

An intelligence official in Miranshah said: "Both of the missiles hit the militants' compound. We are investigating whether there were any high-value targets."

He said that according to initial indications all of the dead were local militants.

But another intelligence official in Miranshah said: "We are investigating a report that there were four Turkmen fighters among the dead."

Officials said earlier this week that a drone strike had killed five German militants.

Charkhel is about 25 kilometres (16 miles) west of Miranshah, in the Dattakhel area.

The United States has massively ramped up its drone campaign in Pakistan's lawless northwest tribal region on the Afghan border, amid intelligence claims of a Mumbai-style terror plot to launch commando attacks on European cities.

The plot was reportedly caught in its early planning stages, according to media reports.

The missile strikes have reached record levels in the past month, killing more than 150 people since September 3, but have also raised tensions with Islamabad amid reported US criticisms of Pakistan's efforts to stamp out the Islamist threat in the area.

Pakistan has said that there was "no justification" for the drone strikes, describing them as "counter-productive" and "a violation of our sovereignty".

Islamabad closed the main border crossing for NATO supply trucks into Afghanistan, where US-led forces are fighting an Islamist insurgency, after at least two of its soldiers were killed in a cross-border helicopter strike.

The United States does not as a rule confirm drone attacks, but its military and the Central Intelligence Agency operating in Afghanistan are the only forces that deploy the pilotless aircraft in the region.

Officials in Washington say previous drone strikes have killed a number of high-value targets, including the former Pakistani Taliban chief Baitullah Mehsud.

Pakistan's ambassador in Washington, Hussein Haqqani, told the BBC that the increase in strikes in North Waziristan came after intelligence agencies uncovered a plot to attack multiple targets in Europe.

The Al-Qaeda plot reportedly targets Britain, France and Germany with a wave of commando-style attacks on key landmarks including Paris's Eiffel Tower and Notre Dame Cathedral and Berlin's Brandenburg Gate.