The beheaded body of a British Red Cross doctor was found by the roadside in southwestern Pakistan Sunday, nearly four months after he was kidnapped by suspected militants.

Police in Quetta, the capital of insurgency-hit Baluchistan province, said a note was found with the body in which the Pakistani Taliban claimed responsibility, saying the doctor had been killed because a ransom had not been paid.

Red Cross officials said 60-year-old Khalil Rasjed Dale had been managing a health program in Quetta, located near the Afghan border, for almost a year when he was kidnapped on January 5. The Red Cross operates clinics in the city that treat people wounded in the war in Afghanistan.

Dale had worked for the Red Cross for years, carrying out assignments in Somalia, Afghanistan and Iraq before coming to Pakistan.

The director-general of the International Committee of the Red Cross, Yves Daccord, condemned the “barbaric act.” He said “all of us at the ICRC and at the British Red Cross share the grief and outrage of Khalil's family and friends.”

British Foreign Secretary William Hague said this was a “senseless and cruel act, targeting someone whose role was to help the people of Pakistan.” He said London had been working tirelessly to secure Dale's release.

The Pakistani government also condemned the killing and vowed to “bring the perpetrators of this heinous crime to justice.”

Also Sunday, U.S. drone strikes killed four suspected militants and wounded at least two others in the restive North Waziristan tribal region bordering Afghanistan.

The strike came as Washington is trying to rebuild diplomatic relations with Islamabad, badly frayed after a cross-border coalition attack mistakenly killed 24 Pakistani troops near the Afghan border last November. Pakistan subsequently shut down the ground supply route to international troops in Afghanistan and demanded an end to U.S. drone strikes, arguing that they are counter-productive because they kill civilians, exacerbate anti-U.S. sentiment and violate sovereignty.

Washington says the strikes are crucial to defeating al-Qaida and the Taliban.