Police from both sides routinely returned fugitives to their respective territories under a 2009 agreement but deportations have grown rarer since President Tsai Ing-wen, who regards Taiwan as a sovereign nation, came to power in 2016.

Beijing, which views the self-ruled island as part of its own territory, has cut off official communication and ramped up pressure on Taipei since Tsai took office.

But on Thursday, the National Immigration Agency said 21 Chinese nationals who entered Taiwan illegally were on the deportation list. It declined to provide additional details, to "ensure smooth and safe operations".

The Chinese nationals were set to be flown out in four groups starting from Wednesday, local news outlet United Daily News reported.

One of the returnees was a man who managed to cross the Taiwan Strait in a rubber dinghy last May.

Taiwan's government said the latest deportations were the first since November 2020 as travel was hampered by the coronavirus pandemic.

"The process ... has positive meanings for normal and orderly exchanges between the two sides," said the Mainland Affairs Council, Taiwan's top body handling China ties.

Thursday's announcement of the deportations comes after China last month returned a Taiwanese murder suspect under the 2009 agreement, which was struck when ties were warmer under Taiwan's then Beijing-friendly government.