South Korea's coastguard said Wednesday it was holding 23 Chinese fishermen in custody for questioning after a violent clash in the Yellow Sea that left one Chinese crew member dead.

The coastguard seized two 93-tonne vessels on Tuesday and towed them to the southwestern port of Mokpo after an operation against some 30 Chinese trawlers it said were fishing illegally in South Korean waters.

"A Chinese consul general interviewed the fishermen one by one after they arrived here this morning," a coastguard spokesman said from Mokpo.

A 44-year-old fisherman was fatally wounded by a rubber bullet after coastguard commandos boarded one of the vessels and were confronted by crew members armed with knives, axes, saws and other weapons.

He was declared dead after being rushed by helicopter to a hospital in Mokpo.

Coastguard officers said they had fired five rubber bullets, with one hitting the chest of the man who wielded a saw.

An autopsy will be conducted to determine if the rubber bullet killed him, Mokpo coastguard chief Kang Seong-Hee told reporters.

"We never fire rubber bullets if they comply with inspections," he said.

The South's foreign ministry expressed regret over the death, while the Chinese embassy in Seoul asked South Korea to investigate it "seriously and thoroughly".

Illegal fishing by Chinese boats is common in South Korean waters, and more than 130 boats have been seized so far this year.

In December 2010 a Chinese boat overturned and sank in the Yellow Sea after ramming a South Korean coast guard vessel. Two Chinese crewmen were killed.

And last December, a coastguard officer was stabbed to death in a struggle with Chinese sailors.