A South Korean coastguard officer died after being stabbed by Chinese sailors who were detained for illegal fishing, a coastguard spokesman said.

A second officer was stabbed and injured during the clash in the Yellow Sea, the spokesman said.

Illegal fishing by Chinese vessels is common in South Korean waters and clashes have become increasingly violent. In September 2008 a South Korean officer drowned while trying to inspect a Chinese boat.

The spokesman said the 41-year-old officer was stabbed after the coastguard detained a Chinese fishing boat 85 kilometres (53 miles) southwest of Socheong island at around 7 am on Monday.

He said it was unclear what weapon was used. The nine Chinese crewmen were detained and were being brought back to shore.

In October the coastguard said it used tear gas and rubber bullets to subdue Chinese fishermen wielding clubs and shovels. Some 21 Chinese were detained but later released after paying a fine.

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

Three Chinese detained after that incident were freed following protests from Beijing.