Rice prices jumped more than 30 % in past few days amid export ban from various countries, raising fears of fresh outbreaks of social unrest across Asia, where the grain is a staple food for more than 2.5 billion people.

The increase came after Egypt, a leading exporter, imposed a formal ban on selling rice to keep local prices down. The Egyptian export ban formalises a previous poorly enforced curb and follows similar restrictions imposed by Vietnam and India. Cambodia, a small seller, has also announced an export ban.

These foreign sales restrictions have removed about a third of the rice traded in the international market.

Rice is also a staple food in Africa, particularly in small countries such as Cameroon, Burkina Faso and Senegal, which have suffered social unrest because of high food prices.