A senior Chinese environmental official has said almost all the chemical barrels that were washed into a major river last week have been recovered.

Vice-Minister of Environmental Protection Wu Xiaoqing told Russian environment officials the operation to clear the barrels from the Wende River in Northeast China was in its final stage and the water quality remained normal, according to a report in Friday's China Environment News.

Wu told Russia's Ministry of Natural Resources and Ecology that 7,107 barrels had been collected and disposed of, including 3,633 that were filled with chemical materials.

Wu said the operation was about to end, although the China Environment News report did not say when exactly it would be called off.

"China has adopted resolute measures to prevent these chemical barrels from floating into Heilongjiang province, and they won't affect Russia at all," Wu was quoted as saying by the paper, which comes under the Ministry of Environmental Protection's administration.

A total of 7,138 chemical barrels were swept into the Wende River, a tributary of the Songhua River, which forms part of China's border with Russia, after floods destroyed two chemical plant warehouses in Jilin city, Jilin province, last week.

A total of 3,662 barrels were filled with colorless and highly explosive chemicals, mainly trimethyl chloro silicane and hexamethyl disilazane.

In another development, Northeast China's Liaoning province has suspended shipping services and tourism on the Yalu River, which marks the border with the Democratic People's Republic of Korea (DPRK), as more rain was forecast to hit the already swollen waterway.

The last two weeks had seen more rains in the river system than at any comparable time in recorded history and more rain was forecast for Thursday and Friday, said a spokesman with the flood control headquarters in the border city of Dandong on the river's lower reaches.

Water levels had risen almost half a meter over one night, said a soldier at a border defense station on Thursday.

City authorities also banned fishing on the swollen river.

Shipping services in neighboring Jilin province on the upper reaches were already suspended, said an official with the headquarters, but he did not say when the services were stopped.

More than 40,000 residents had been evacuated from the homes in Dandong by Thursday and authorities had blocked all the gates on dike walls that separate the riverside from the downtown area, said the headquarters.

Some of the evacuated residents were moved to schools on higher ground and others moved into relatives' homes.

The city has mobilized 43,000 soldiers, civil servants and residents to fight the floods.

The Tumen River, also bordering the DPRK, in neighboring Jilin province, has also seen record water levels in the past two weeks,

The Yanbian Korean autonomous prefecture, which borders the DPRK by the Tumen River and is home to a large ethnic Korean population, has suffered the worst floods in 100 years this year, with nearly a quarter of its 2.18 million residents affected, according to the Yanbian government.

In Yanbian, torrential rains and floods have destroyed 6,847 houses and forced the evacuation of more than 86,000 people, the prefecture government said on Wednesday.

At least 74 people have died in heavy flooding in Jilin over the past two months, and 71 are missing.

As of Wednesday, rain-triggered floods had left 1,072 people dead and 619 missing this year in the whole country, according to the State Flood Control and Drought Relief Headquarters.