Amid ongoing incidents of self-immolation in Tibet, the US has asked Tibetans to end the voluntary sacrifice and called on the Chinese government to permit them to express grievances freely, publicly, peacefully and without fear of retribution.

"We remain concerned by the deteriorating human rights situation in Tibetan areas, including the numerous tragic self-immolations that have occurred and related reports of detentions and arrests," state department spokesman Patrick Ventrell told reporters on Friday.

"We've also seen, in Nepal, self-immolations. We continue to call on the Chinese Government to permit Tibetans to express grievances freely, publicly, peacefully, and without fear of retribution. And we urge Tibetans to end self-immolations," Ventrell said in response to a question.

The US statement came amidst reports that security officials in northwestern Chinese province of Gansu have arrested five Tibetans and accused them of inciting a series of self-immolations late last year by convincing participants that they would become heroes in death.

Four of those detained were Buddhist monks, who the police said were guided by a Tibetan exile organisation, The New York Times reported.