US Secretary of State Hillary Clinton on Thursday appealed for Pakistan, Afghanistan and other Muslim-majority nations to respect religious minorities, saying some are treated "brutally."

"This is one of our biggest problems in the world right now. There needs to be a greater acceptance of religious tolerance and in so many places there is no history of religious tolerance," Clinton told the House Foreign Affairs Committee.

Clinton was responding to a question from Representative Chris Smith, who voiced concern about Christians, Hindus and other religious minorities in Afghanistan, Pakistan and Egypt.

The problem was "not only against Christians or against Hindus, it's also against different sects of Muslims," the top US diplomat said.

"There are Islamic sects in Afghanistan and Pakistan and elsewhere -- they're discriminated against, persecuted and their adherents brutally treated."

Pakistan has witnessed a wave of violence against minorities including members of the Ahmadi sect, whom Pakistan declared as non-Muslims in 1974. The independent Human Rights Commission of Pakistan said 418 people were killed last year in violence between rival Muslim communities.

Smith also voiced concern about the safety in China of Chen Guangcheng, a blind, self-taught lawyer who was jailed for more than four years after exposing abuses in China's one-child policy.

"We hear he may have been beaten to death. We don't know. But please, call the foreign minister (of China) on that, if you would, Madam Secretary," Smith said.

Clinton promised to follow up on his concerns.

Chen earlier this year managed to smuggle out of his home a self-made video in which he said he was under "illegal" house arrest. Activists say that police retaliated by beating both Chen and his wife, Yuan Weijing.

Two Chinese activists -- including a Buddhist nun -- said they were robbed and beaten last month as they tried to reach Chen's home in eastern China.