China on Monday said it had respected the rights of a dissident activist who died under detention, provoking outrage from her lawyer who maintains police denied her medical treatment for months.

Cao Shunli, 52, died on Friday after police detained her and denied her medical treatment for several months after she fell ill, her brother and lawyers acting on her behalf told AFP.

Countries including the US, Britain, France and Canada expressed concern at Cao's death, while the UN's human rights office called for a full review of her detention.

China's foreign ministry spokesman Hong Lei said that Cao's "lawful rights and interests have been protected in accordance with law", without giving details.

He also expressed "strong dissatisfaction," with international comments on Cao's death.

"We oppose other countries interference in China's judicial sovereignty and independence under the pretext of human rights," he said.

The foreign ministry's statement was met with outrage by Liu Weiguo, one of Cao's lawyers.

"No matter how the government explains it, the fact that Cao Shunli died because she was not given medical treatment in time cannot be denied," Liu said. "Her right to medical treatment should have been respected."

There were no immediate plans for a funeral, Liu added. "The family wants her body to be kept in cold storage for now and will only hold a funeral once the reason for her death has been clearly checked," he said.

Cao was set to travel to Switzerland last September to observe a UN Human Rights Council review, but police detained her at Beijing's international airport, Wang Yu, her other lawyer, told AFP.

She became ill in November but police denied her access to medical treatment for more than three months, sending her to hospital only when she fell unconscious after suffering organ failure in late February, Wang said.

Cao, a law graduate from one of Beijing's top universities, had engaged in peaceful activism for several years, according to reports.

She had joined a rare protest outside China's foreign ministry last year to demand greater citizen participation in the UN's review of human rights in China, according to Amnesty and other rights groups.

European countries and the United States regularly condemn China on human rights, citing cases including its jailing of dissidents.

Beijing argues that its citizens enjoy increasing freedoms thanks to decades of rising prosperity.