China on Sunday said it would step up law enforcement patrols in waters near Taiwan after two Chinese nationals died in a boat incident involving Taiwan’s coast guard.

A Chinese boat was carrying four people when it capsized on Wednesday near the Kinmen islands while pursued by the Taiwanese coast guard.

All four on board were thrown into the water and two of the crew later died.

The Chinese coast guard said it would “carry out regular law enforcement patrol operations” in the area.

The patrols are intended to “further maintain the order of operations in relevant waters and protect the safety of fishermen’s lives,” Gan Yu, a spokesperson for the Chinese coast guard, said in a statement.

China has condemned democratic Taiwan for the incident and urged the island to release the two surviving members of the boat crew, who were detained.

Taipei in turn blamed Beijing, saying the boat was “within prohibited waters” around the Kinmen islands — a territory administered by Taiwan but located just five kilometres from China’s city of Xiamen.

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

Beijing claims Taiwan as part of its territory and has vowed to one day bring the self-ruled island under its control.

Taiwan’s presidential election, held in January, was won by the Democratic Progressive Party’s Lai Ching-te, whom Beijing considers a “separatist”.

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

And Beijing has stepped up its military presence near Taiwan, deploying warplanes and naval vessels around the island on a nearly daily basis.