Authorities in the central region's Quang Ngai Province have called for help in dealing with the oil spill from a shipwreck that happened on Sunday.
Nguyen Hoang Son, vice chairman of the province's People's Committee, said in an emergency statement that the oil "has spread widely to around seven sea miles from the Hoang Son South and can severely pollute the environment."
The accident happened as the cargo ship hit a coral reef on its way from Thailand to Vietnam's Hai Phong city, sinking around 18 kilometers from the Ly Son Island off the provincial coast.
"When the boat sank, there was still around 180 tons of oil that couldn't be transferred to rescue boats because of strong waves," Son said.
Rescuers had managed to transfer 40 tons of diesel oil, 12,870 tons of corn seeds and 850 barrels of paint from the boat, and save all 23 crew members.
Ten fishing and passengers boats were sent out to save the sailors after receiving their May Day signals.
Also on Sunday, a fishing boat from Quang Ngai Province received help 15 days after its 16 member crew were trapped at sea.
The engine of their boat had broken down in waters off the Hoang Sa (Paracel) Islands.
Rough waters had made it difficult to approach the troubled boat.
The boat was towed to shore by another boat owned by local fisherman Phung Thoai and reached the shore safely on Tuesday evening.