Water monitoring devices and 150 tonnes of activated carbon were sent to Russia on Wednesday, spokesman Qin Gang said, adding foreign ministry and environmental officials on both sides of the border were sharing information and had set up hot lines. "We have reported in a timely manner to Russia the water quality and the results of our observations," Qin told a regular news briefing.
"We will proceed from the principle and spirit of friendly cooperation and keep close cooperation with the Russian side to minimise the possible impact of pollution on the Russian side," he said.
An explosion at a chemical plant in northeastern China in November poured 100 tonnes of cancer-causing benzene compounds into the Songhua River near the city of Harbin.
Officials shut off the water in Harbin, a city of 9 million, in response. The 80-km (50-mile) slick has since passed the city but is heading northeast through Heilongjiang province toward the Russian border.
Qin said China had not offered Russia compensation for the environmental disaster.
"As far as I know the two sides have not yet entered into a discussion of this nature," he said.
On Thursday the slick had passed through the Heilongjiang counties of Mulan and Tonghe, but local officials said both areas relied on underground water sources, not the river, for their supply and water there had not been cut off.
Cold weather that froze parts of the river was slowing its flow, Xinhua news agency reported, adding areas downstream were being supplied with monitoring equipment in preparation for the arrival of the slick.