Two Tibetan cousins set themselves on fire in northwest China to protest against Beijing's hardline rule, taking the total number of self-immolations last week to seven, a London-based rights group said.

The two men, identified as Tsepo, 20 and Tenzin, 25, called for independence for Tibet as they set themselves ablaze in front of a government building in their village, north of regional capital Lhasa on Thursday, Free Tibet said.

One of the cousins died as he was being taken to hospital but the whereabouts and condition of the other was not immediately known, the group said in a statement on Saturday.

"It has taken two days for information about this latest protest to emerge," Free Tibet director Stephanie Brigden said.

"Chinese state security forces have been deployed in large numbers across (the area)... Tibetans are afraid to talk about what is happening because they fear that their communications are being monitored by the government."

Calls to government and police offices in Driru county, where the incident occurred, went unanswered Sunday.

Last week saw a total of seven self-immolation incidents, a significant number since the latest wave of anti-China protests erupted in the region.

About 60 ethnic Tibetans, many of them monks and nuns, have set themselves on fire in China since February 2009 to protest against Beijing's rule in Tibet. Only a small minority are thought to have survived.

Many Tibetans in China accuse the government of enacting religious repression and eroding their culture, as the country's majority Han ethnic group increasingly moves into historically Tibetan areas.

China rejects this, saying Tibetans enjoy religious freedom. Beijing points to huge ongoing investment it says has brought modernisation and a better standard of living to Tibet.