Forty specialized vessels and about 800 fishing boats are rushing to mop up a major oil slick off China's northeast coast before Saturday, in a bid to prevent the contamination of international waters, local officials said Tuesday.

Photo taken on July 19, 2010 shows the polluted sea area affected by oil leakage in Dalian, a coastal city in northeast China's Liaoning Province. Over 500 fishing boats Monday joined a massive oil spill clean-up operation underway off the coast of Dalian City, three days after pipelines exploded near the city's oil reserve base, one of China's largest. [Xinhua]

"Our priority is to collect the spilled oil within five days to reduce the possibility of contaminating international waters," Dai Yulin, vice mayor of Dalian City, Liaoning Province, told Xinhua.

He said maritime agencies have set up 40 monitoring stations to watch over a 1,500-square-kilometer area off the city's coast.

Dai said four specialized vessels will arrive in Dalian by tonight bringing the number of oil-spill-control vessels in the area to 40.

More than a thousand boats joined the ocean cleanup which started last Saturday. But many of the 800 fishing boats that had joined in the work stopped Tuesday on account of heavy rains and strong winds.

Two crude oil pipelines exploded in Dalian's Xingang port late last Friday. The spectacular blaze was extinguished after 15 hours but the blasts caused an oil slick that had stretched for 183-square kilometers off the Dalian coast by Tuesday.

Officials said they did not know the exact amount of oil spilled into the sea.