Taiwan's top China policy body criticised Beijing after its civil aviation authority opened another west-to-east connecting route above the sensitive waterway.

China has shown "complete disregard for the consensus of both sides and Taiwan's public opinion, using unilateral actions to change the status quo and increase cross-strait and regional unease", Taiwan's Mainland Affairs Council said.

Beijing adjusted the M503 north-to-south route through the Taiwan Strait in January 2024 and opened two west-to-east connecting flight paths months later.

The newly-activated west-to-east route is intended to "alleviate the pressure caused by the increase of flights", China's Taiwan Affairs Office spokesman Chen Binhua said Sunday, quoted by state news agency Xinhua.

But Taipei's Mainland Affairs Council denied there had been an increase in air traffic.

It said China had "unilaterally violated the consensus" three times by launching the routes without consulting Taiwan and urged Beijing to engage in negotiations.

"The current cross-strait and Asia-Pacific situation is complex, the Mainland's unilateral actions will escalate regional tensions, which no party wishes to see," the Council said.

Beijing insists democratic Taiwan is part of its territory and has never renounced the use of force to bring the self-ruled island under its control.

Beijing regularly deploys fighter jets, warships and coast guard ships near Taiwan, and has held several major military exercises around the island in recent years.