Nighttime tide watching has been banned along the Qiantang River in east China's Hangzhou City where at least 12 people were killed by a tidal wave last week.

"Tide watching is strictly forbidden at night and billboards must be erected along the Qiantang River to warn people about the danger of swimming in the river and playing on the bank," said a circular issued by the government of Hangzhou, capital of Zhejiang Province.

All districts along the river must carry out thorough checkups to identify dangerous sites. Barriers must be established around the sites and patrolling should be reinforced, the order said.

Departments in charge of public security, traffic, maritime, meteorology, security supervision and propaganda have been told to treat the tragedy as a lesson and to improve their work in order to prevent such an accident from happening again.

The order was made after a rising tide at the mouth of the Qiantang River mouth dragged more than 30 tourists out to the sea on Thursday.

Six men and six women have been found dead and 22 others were rescued. At least one of the fatalities was a child.

It is hard to verify the total death toll as some of the victims might have been visiting on their own and therefore may not have been reported missing.

The river, boasting huge tides twice every month and tidal currents twice a day, has been a famous tourist attraction since ancient time.

The trumpet-shaped levees on the river are especially dangerous as the waves can reach as high as 3.5 meters and its power could reach up to four to seven tons per cubic meter, experts say.

The worst accident on the Qiantang occurred in October 1993, when 19 people died after being swept out to sea.

(Xinhua News Agency August 7, 2007)