PESHAWAR, Pakistan At least three suspected Islamist militants were killed and two wounded by an explosion in a Pakistani tribal region regarded as a hotbed of support for al Qaeda and the Taliban, officials said.
Officials, speaking on condition of anonymity because of the sensitivity of the matter, gave starkly differing accounts of what caused the blast in a house in Saidgai, a village 15 km (10 miles) north of Wana, the main town in North Waziristan.
A senior military official said the militants were killed while making bombs.
However, an intelligence official said the explosion was caused by a missile fired from a pilotless drone aircraft operated by U.S. forces in Afghanistan.
"The missile was probably fired by a U.S. drone," he told Reuters.
The intelligence official said four people were killed, including two Afghans and two Pakistanis.
If it was a U.S. drone attack, it wouldn't be the first time Pakistani military officials have stuck by a version suggesting bomb materials in a house used by militants had exploded.
Pakistan's public stance is that it will not allow its territorial sovereignty to be violated by foreign forces stationed in Afghanistan.
The explosion happened in a house surrounded by a walled compound next to a religious school, or madrasa, run by a pro-Taliban cleric, Maulana Noor Mohammad.
The intelligence officer said Mohammad used it as a "guest house".
In January last year, a helicopter gunship attack killed eight of the cleric's family, and two months later Pakistani helicopter gunships and ground forces launched an attack in Saidgai, that killed around 45 militants, mostly foreigners.
Many al Qaeda-linked fighters, including Uzbeks, Chechens and Arabs, fled to Pakistan's lawless tribal belt, close to the Afghan border, after U.S.-led forces toppled the Taliban regime in Afghanistan in 2001.
Pakistani security forces launched a series of operations in North and neighboring South Waziristan in recent years to drive out foreign insurgents, but the government then struck peace deals in the hope of marginalizing them.
Last month, pro-Taliban tribesmen, backed by Pakistani troops, began fighting foreign militants in South Waziristan. More than 300 foreigners and up to 40 tribal fighters were killed during the fighting.
President Pervez Musharraf, a staunch ally in the U.S.-led war on terrorism, earlier this month said there were indications tribesmen in North Waziristan and Bajaur, another hotbed of support for the militants, would also turn against the foreign fighters.