Taiwan called on Beijing Thursday to restrain its citizens from illegal fishing in the waters around the self-ruled island, defending its coast guard over the pursuit of a boat that led to the deaths of two Chinese nationals. 

The boat was carrying four people when it capsized near the Kinmen islands -- a territory administered by Taiwan but located just five kilometers (three miles) from China's Xiamen. 

All four people were thrown into the water, and two of the crew later died, according to Taiwan's coast guard.

China -- which claims Taiwan as part of its territory -- condemned the democratically ruled island for the incident Wednesday, saying it "severely harmed the feelings of compatriots on both sides of the Taiwan Strait". 

But Taiwan's Coast Guard Administration said the speedboat was "0.86 nautical miles within prohibited waters", and that after the capsizing, its personnel had immediately conducted search-and-rescue operations. 

The Mainland Affairs Council (MAC) -- Taiwan's official body dealing with China affairs -- defended the coast guard Thursday, saying their procedure was "not improper". 

MAC also placed the blame across the strait, saying that in recent years, Taiwanese authorities have seen Chinese people crossing the border and engaging in "sand-dredging, fishing with explosives and poisons, and discarding garbage". 

"Despite our calls to strengthen governance, there has been no improvement," it said. 

"Recently many Chinese fishing boats have continued to enter our restricted or prohibited waters, taking advantage of the Lunar New Year to catch high-value fish," it added, referring to a holiday period for both Taiwan and China.

"We deeply regret that the Chinese crew refused to cooperate with our law enforcement work and this unfortunate incident occurred," it said. 

"We also hope the mainland authorities can restrain similar behaviours of the people on the other side."

The two rescued crew members were brought to Kinmen for investigation, while the families of the deceased will be notified about the incident "through channels", the coast guard said. 

China does not rule out the use of force to bring the self-ruled island under its control, and has since 2016 cut off high-level communications with Taipei as President Tsai Ing-wen has refused to acknowledge Beijing's claim on Taiwan. 

Wednesday's incident comes against a backdrop of heightened tensions across the Taiwan Strait.

Taiwan's presidential election, held in January, was won by Tsai's deputy, Lai Ching-te, who Beijing regards as a "separatist". 

Chinese President Xi Jinping has ramped up rhetoric in recent years for the "unification" of Taiwan with China.