China's top legislature on Thursday passed an amended water pollution law that toughens punishment of company officials through hefty fines.

The Water Pollution Prevention and Control Law, to take effect on June 1, was passed at the 32nd session of the Standing Committee of the National People's Congress (NPC), which concluded here on Thursday.

"Enterprise heads directly responsible for causing severe water pollution incidents and others with direct responsibility would be fined up to half of their income in the previous year," said the law.

Previously, corporate executives faced only administrative penalties.

Water pollution is among the top environmental concerns of the Chinese government and the public.

A 2006 survey found that surface water generally was classified as containing intermediate levels of pollution, but one third of the 744 samples tested were graded at the worst pollution rating.