ISLAMABAD, Pakistan (AP) – A missile strike by a suspected U.S. drone killed at least six people in a Pakistani tribal region near the Afghan border, two Pakistani intelligence officials said Wednesday.

American forces recently ramped up cross-border operations against Taliban and al-Qaeda militants in Pakistan’s wild border zone, a possible hiding place for Osama bin Laden.

The attacks have drawn stiff protests from Islamabad, an uneasy ally in Washington’s seven-year war on terror, particularly since a highly unusual Sept. 3 raid by U.S. ground troops in the South Waziristan region.

The two intelligence officials said the missiles struck the home of a local Taliban commander before midnight Tuesday near Mir Ali, a town in the North Waziristan region.

The officials, citing reports from their field agents, said six people were killed in the attack. Both officials asked for anonymity because they were not authorized to speak to media.

They said a U.S. drone aircraft, not Pakistani forces, fired the missiles. They did not identify any of the victims.

Pakistani leaders insist only their forces are allowed to carry out operations inside Pakistan, and its troops recently fired warning shots at U.S. helicopters flying over the ill-marked frontier.

Meanwhile, a doctor for the Taliban and a spokesman for the group denied reports that the movement’s top leader in Pakistan, Baitullah Mehsud, had fallen ill and died.

“I spoke to him today at 9 a.m. on the telephone, and he told me that he is surprised over rumors about his death,” physician Eisa Khan told The Associated Press.

Khan said Mehsud had an unspecified kidney problem, but gave no more details. Mehsud’s spokesman, Maulvi Umar, was cited on Geo television station as saying he was healthy.

Officials have accused Mehsud of being behind a wave of suicide attacks in Pakistan since the middle of last year, including the slaying of opposition leader Benazir Bhutto in December.

American officials express frustration at Pakistan’s failure to kill or capture militant leaders whom they accuse of sending fighters and arms into Afghanistan, where foreign troop casualties are escalating.

In a move that could help answer those complaints, Pakistan’s army chief appointed a new head of the country’s premier intelligence agency on Monday.

U.S. and Afghan officials have accused elements in the Inter- Services Intelligence agency of secretly colluding with some militant groups.