China defended its human rights record to the UN on Tuesday, insisting it was abiding by its obligations, but activists urged an end to crackdowns on dissidents and minorities.

China's envoy Wu Hailong acknowledged his country still faced "challenges" but told the UN Human Rights Council it had lived up to pledges made when it was last scrutinised by the watchdog.

In 2009, the council urged Beijing to do more to reduce poverty, introduce judicial and political reforms and respect the rights of ethnic minorities.

"The above recommendations either have been implemented or are being carried out, and our commitment has been basically fulfilled," Wu said.

But he acknowledged that China still "faces many difficulties and challenges in promoting and protecting human rights".

All 193 UN member states are meant to undergo four-yearly reviews of their rights record.

In the run-up to China's review, campaigners and Western officials raised the alarm about the disappearance of Chinese activist Cao Shunli, who had been due in Geneva.

Her whereabouts are still unknown, said Sharon Hom, executive director of the US-based Human Rights in China, who accused Beijing of "mouthing openness to criticism" without genuinely acknowledging failings.

China's ruling Communist party has pulled millions of people out of poverty thanks to strong economic growth, but critics say political reforms have not kept up with economic advances.

US-based Human Rights Watch urged China to demonstrate its commitment to human rights by ending harassment, arbitrary arrest and torture of activists.

"China is good about signing human rights treaties, but terrible about putting them into practice," said its China director Sophie Richardson.

Human Rights Watch also urged Beijing to improve media freedom and halt abuses against its Tibetan and Muslim Uighur ethnic minorities.

About 120 ethnic Tibetans have set themselves on fire in China since 2009 to protest against Chinese rule of Tibetan areas.

Rights groups blame religious repression and cultural erosion, while Beijing says it has brought massive investment to the relatively undeveloped region.

Pema Yoko, deputy director of Students for a Free Tibet, on Tuesday rejected Wu's claims and told AFP it was normal for China to "blatantly lie".

Chimey Nelung, spokesman for the Tibetan Youth Association in Europe, said it was crucial for the international community to "confront the Chinese about their human rights situation".

At the review, US delegate Uzra Zeya spotlighted the harassment, detention and punishment of human rights activists and their relatives.

"We are concerned that China suppresses freedoms of assembly, association, religion, and expression, including on the Internet," she added.

Defending China's record, Wu pointed out that the number of crimes carrying the death penalty had been reduced.

China has halved its number of executions since 2007, but still puts an estimated 4,000 people to death every year.

Hanns Schumacher, Germany's ambassador, and other European delegates welcomed that move, but said it was time to impose at least a moratorium on capital punishment.

"Enormous economic progress and many legal improvements protecting the right of individuals in China go hand in hand," said Schumacher.

"We encourage China to continue on this path," he added, calling for legal reforms to protect freedom of expression, abolish labour camps and protect minority rights.

Western ambassadors also urged China to sign an international accord on civil and political rights and allow UN human rights monitors to visit Tibetan and Uighur areas.

Four Tibetan activists hammered their message home by scaling scaffolding on the UN building in Geneva and unfurling a massive banner reading: "China Fails Human Rights, UN stand up for Tibet."

UN security swiftly cut down the banner and arrested the protesters, but also grabbed journalists' press passes and ushered them away.

"The Chinese government must answer for its brutality and atrocities in Tibet," exiled monk Sungjang Rinpoche told AFP.

Uighur exile Omar Kanat, meanwhile, complained about China's broadbrush use of the "terrorist" label for activists from his Muslim community and slammed restrictions on religious and cultural freedom.

He said he feared that Beijing was pushing the Uighurs to "rise up", and thereby create an excuse for an even harsher crackdown.