Seoul urged Beijing Tuesday to crack down on illegal fishing and growing violence by Chinese boat crews, after China's foreign ministry expressed regret over the killing of a coastguard officer.

The South Korean officer was fatally stabbed on Monday, and a colleague wounded, as he tried to arrest the skipper of a Chinese boat in the rich fishing grounds of the Yellow Sea.

The incident has sparked widespread anger in South Korea.

"Although they have expressed regret, what we find more significant is that such an unfortunate event should never take place again," said a spokeswoman for Seoul's foreign ministry.

"We urge the Chinese government to take necessary measures to root out illegal fishing and violence by Chinese fishermen."

It was the second time in less than four years that a South Korean coastguard officer had been killed trying to detain a Chinese boat.

The coastguard says that Chinese crews use weapons including axes, hammers and bamboo spears to try to escape arrest. Some 475 Chinese boats have been seized so far this year, compared with 370 in the whole of last year.

Newspapers and politicians angrily condemned China's initial response Monday to the incident, which did not include any apology.

More than 100 people -- including a driver who rammed his car repeatedly into a police bus -- protested outside Beijing's embassy. "Is China a Neighbour or a Pirate?" read one placard.

Another group later burned a Chinese flag outside the mission.

The 42-year-old boat captain was being questioned Tuesday in the western port of Incheon as the coastguard sought a formal arrest warrant against him for murder and violating the South's exclusive economic zone.

Eight of his crewmen are accused of obstruction.

"The captain has denied stabbing the officers. But we have firm evidence including his bloodstained clothes... so we won't have much problem charging him," a coastguard spokesman told AFP.

Officials quoted by Yonhap news agency said they believed the captain had stabbed the 41-year-old victim with two knives, which were fingerprinted.

Seoul summoned China's ambassador Monday to deliver a strong protest.

"The Chinese side regrets that the relevant incident caused the death of an ROK (Republic of Korea) coastguard, which is an unfortunate event," said Chinese foreign ministry spokesman Liu Weimin in Beijing on Tuesday.

President Lee Myung-Bak ordered officials to get tough with illegal fishermen by better equipping the coastguard and deploying more personnel.

"They were not fishermen but pirates," said the front-page headline of JoongAng Ilbo newspaper.

"Without long-term measures, this incident threatens to trigger the worst-ever diplomatic row between the two nations," it added in an editorial.

The Chosun Ilbo newspaper, quoting an unidentified senior Seoul official, said that Lee's planned visit to China in January might be postponed unless Beijing comes up with firm solutions.

"China offered neither apology nor words of condolence for our coastguard officer... we should act strongly against these modern-day pirates," Hwang Woo-Yea, floor leader of the ruling Grand National Party, told lawmakers before Tuesday's statement from Beijing.

Pollution and overfishing at home have pushed more Chinese fishing boats to poach in South Korean waters.

A Chinese boat fishing for croakers, anchovies, crabs and shrimps can earn about 30 million won ($25,985) during a two-week voyage, but faces a fine of 50-100 million won if caught.

The coastguard said it would use firearms "more aggressively" in future rather than as a last resort.