China's Taiwan Affairs Office said Taiwan had for some time been treating Chinese fishermen in a "rough and dangerous" manner, which was the main reason for the "wicked" incident.

Taiwan, which China claims as its own territory, has complained in recent years about Chinese fishing boats and other vessels operating in Taiwan-controlled waters, especially around the Kinmen and Matsu islands which sit a short distance from China's coast.

On Wednesday, two out of four people on a Chinese speedboat which entered prohibited waters near Kinmen's Beiding islet, home to a military garrison, died when their boat overturned after it tried to flee from a Taiwanese coast guard vessel, the coast guard said.

Taiwan's Chinese-policy making Mainland Affairs Council said that according to a preliminary investigation, the coast guard performed their duties in accordance with the law and did nothing improper.

It is China which has failed to stop Chinese ships illegally dredging for sand, using explosives and poison to fish and dump garbage in Taiwanese waters and the situation has not improved despite complaints, the council said.

"We deeply regret that the mainland crew members refused to cooperate with our law enforcement work this time and an unfortunate incident occurred," it said in a statement.

"We also hope that the relevant mainland authorities can restrain similar behaviour by people on the other side" of the Taiwan Strait, the council added.

Kinmen was the site of frequent fighting during the height of the Cold War but is today a popular tourist destination, though many of the islets which are part of the island group are heavily fortified by Taiwan's military and off limits to civilians.

Taiwan, whose government rejects Beijing's sovereignty claims, says China has been using so-called grey-zone warfare, which entails using irregular tactics to exhaust a foe without actually resorting to open combat, including sending civilian ships into or close by Taiwanese waters.