Among measures announced are the deployment of a 100,000-member anti-terrorist force, along with anti-aircraft missile batteries near to key locations.

Farmers killed

The Kunming explosions come two days after police in the same province, Yunan, opened fire and killed two rubber farmers in a clash that also saw 41 police officers injured.

The clash was sparked when police tried to arrest five people for allegedly attacking a local rubber company in a long-running dispute between farmers and the firm, state media said.

Chinese authorities have ordered local officials to keep a lid on grievances and try to resolve disputes to ensure a "harmonious social atmosphere" in the Olympics period.