A prominent scientist who helped Pakistan become a nuclear power and has been a public supporter of Afghanistan's Taliban regime has been detained by Pakistani authorities, his family said Wednesday.

The government said Sultan Bashiru-Din Mehmood had been placed in protective custody.

Mehmood's relatives said he was arrested Tuesday by intelligence officials.

"We don't know on what charges," said Asim Mehmood, the scientist's son. He said at least two other scientists, friends of his father, were also arrested Tuesday in Lahore.

Mehmood informed his family that he is safe, his son said.

Family members said he had been working recently on projects in Afghanistan, including land development, educational reform and ways to feed the impoverished population.

Pakistani authorities would not discuss the reasons for the detentions, saying only that Mehmood and the others were in protective custody. The law gives authorities wide latitude to detain people without charges.

Officials at the Pakistan Atomic Energy Commission said Mehmood had been a project director for the nation's nuclear program and remained in key positions until his retirement last year.

Abdul Majid, one of the other detainees, also worked with Mehmood for years at the atomic energy commission.

Mehmood's links with Islamic groups and his pro-Taliban sentiments had drawn scrutiny from Pakistani security agencies in recent months, sources at the energy commission said, speaking on condition of anonymity.

Mehmood addressed a gathering of intellectuals last week and proposed a three-month cease-fire to resolve the situation in Afghanistan. He had urged the United States to halt airstrikes so negotiations could take place.

Islamic militants have staged mass demonstrations in Pakistan since U.S.-led airstrikes against Afghanistan began Oct. 7. Some Islamic militant leaders have condemned President Gen. Pervez Musharraf's decision to support the United States and say his government's days are numbered.

Political unrest in Pakistan is particularly alarming to the international community because the country, like neighbor and rival India, is a nuclear power with a lethal arsenal of weapons.

Asim Mehmood said his father is loyal to Pakistan and "never told a lie in his life."

"He has always worked for the betterment of the country," Asim said.

Mehmood won Pakistan's prestigious Sitar-e-Imtiaz award in 1998.