Rice prices jumped 30 per cent to an all-time high on Thursday, raising fears of fresh outbreaks of social unrest across Asia where the grain is a staple food for more than 2.5bn people.

The increase came after Egypt, a leading exporter, imposed a formal ban on selling rice abroad to keep local prices down, and the Philippines announced plans for a major purchase of the grain in the international market to boost supplies. Global rice stocks are at their lowest since 1976.

Independence protesters burned shops and cars in the Tibetan capital Lhasa on Friday and Chinese police were reported to have shot dead at least two people, in the fiercest unrest in the region for two decades.

China accused followers of the Dalai Lama of “masterminding” the uprising, which shatters its carefully-cultivated image of national harmony in the buildup to the Beijing Olympic Games.

A spokesman for the exiled Tibetan spiritual leader called the allegation “absolutely baseless”. The Dalai Lama appealed to China to stop using force and begin dialogue. Similar protests in the past have been crushed with gunfire and mass arrests.