China expressed regret on Wednesday after a woman protesting against a controversial Chinese-backed copper mine in Myanmar was shot dead.

The woman, believed to be in her 50s, was gunned down Monday when police opened fire on local protesters, in the latest dispute involving a Chinese project in the country.

"We express concern and regret about the casualty," Chinese foreign ministry spokesman Hua Chunying told a regular press conference.

"We encourage Chinese companies to abide by local laws," she added.

The mine has triggered fierce opposition from local villagers due to alleged land grabs and environmental damage. It has raised questions about Myanmar's reliance on investment from neighbouring China -- which gave crucial political support to the former junta.

China's Wanbao, a government owned firm which runs the project as part of a joint venture with a major Myanmar military conglomerate, said the woman's "senseless death" was "painful and poignant".

Beijing was a key backer of Myanmar's military junta while it was under Western sanctions, but President Thein Sein has increased ties with other countries including the United States since launching political reforms in 2011.

Protests against the huge $3.6-billion Chinese-backed Myitsone Dam led Thein Sein to suspend the project in 2012, sparking anger in Beijing.

Wanbao said it had completed two major consultations this year in a process of "reconciliation" with local people while the project remains on hold.

In November 2012 a botched police raid using phosphorus on a protest at the mine left dozens of people, including monks, with burn injuries.

That crackdown, the harshest since the end of outright army rule in 2011, sparked fury in the Buddhist-majority country.

Earlier this year two Chinese workers were kidnapped at the site by activists, though they were later released unharmed.

Myanmar state media reported Monday that nine protesters and 11 police officers had also been injured during the protest.