BEIJING, Oct 20, SPA-- China criticised Vietnam on Wednesday for inviting bids for oil exploration in the disputed Spratly islands, saying the plan violated China's sovereignty and sea rights. A statement on the Foreign Ministry's Web site called on Vietnam not to take unilateral action which would complicate and broaden the dispute over the Spratlys, over which China claims sovereignty. "China has serious concerns and is strongly dissatisfied and has made representations with the Vietnamese side," Foreign Ministry spokeswoman Zhang Qiyue was quoted as saying on the Web site. China, Taiwan and Vietnam claim the whole of the Spratlys -- a cluster of rocks in the South China Sea believed to be rich in oil, gas and minerals -- while Malaysia, Brunei and the Philippines claim portions of the islands. China has in past called Vietnam's plans for commercial flights to the Spratlys "illegal and invalid". Vietnam, in turn, has expressed concern over an agreement between the Philippines and China to explore for oil and gas there. China has been stepping up efforts to develop resources to feed the demands of its booming economy and is engaged in similar dispute with Japan, which has requesting Chinese firms cease exploration for natural gas in a disputed area of the East China Sea. --SPA 2233 Local Time 1933 GMT www.spa.gov.sa/212306