TAIPEI, Taiwan– Taiwan's defence ministry said late Thursday that 20 Chinese military aircraft had been detected since nightfall, a rise in activity following a large number of planes spotted earlier in the day.

Beijing claims democratic Taiwan as part of its territory, and has never renounced the use of force to bring it under China's control.

China has stepped up military pressures on Taiwan since 2016 after President Tsai Ing-wen was elected, sending in warplanes and other military aircraft while Chinese ships maintain a near-constant presence around its waters.

In the 24 hours leading up to 6:00 am Thursday (2200 GMT Wednesday), the Ministry of National Defence said it had detected 32 Chinese aircraft and five naval vessels operating around Taiwan.

Twenty of the aircraft "crossed the median line of the Taiwan Strait", it added in a statement.

The highest number this year -- 33 warplanes -- were detected in two other 24-hour periods in late January and early February.

Later at night, the ministry announced that "20 PLA aircraft... were detected from 1930 hr (1130 GMT)".

They included fighter jets, unmanned drones, and medium-range transport aircrafts, according to a tweet on the ministry's official X account.

Among the 20, "nine crossed the median line of the Taiwan Strait and entered the north, central and south parts of Taiwan's (air defence identification zone)", it said.

Relations between both sides of the Taiwan Strait have been frosty since Tsai's election in 2016, with Beijing cutting off high-level communications due to her refusal to acknowledge China's claim.

Her deputy Lai Ching-te was elected as president in January, despite warnings from Beijing that he was a "dangerous separatist".

Lai and vice president-elect Hsiao Bi-khim of the ruling Democratic Progressive Party (DPP) will take office on May 20.

China's Taiwan Affairs Office on Tuesday slammed Hsiao over her visit to the Czech Republic, saying it served "the purpose of Taiwan independence... and is unhelpful for peace and stability in the Taiwan Strait."

She appeared to be at the European Parliament on Thursday, according to a picture posted on X by Andrus Ansip, an Estonian politician and member of the parliament.

- Fishing boat row -

Adding to tensions, a row between Taipei and Beijing over a fatal fishing boat incident has dragged on since last month.

A Chinese speedboat carrying four people capsized on February 14 near Taiwan's Kinmen islands while being pursued by the Taiwanese coast guard, killing two people while the other two survived.

Beijing has accused Taiwanese authorities of "seeking to evade their responsibilities and hide the truth" about the incident, while a Taiwanese coast guard official has said the boat involved was zigzagging and "lost its balance" before capsizing.

China has said it will step up patrols around Kinmen following a series of deadly incidents, including the sinking of another boat in the area this month that resulted in the deaths of two crew members.

Last month, Taiwan said 11 Chinese naval vessels were detected around Taiwan, the most this year.

Taiwan also detected a record eight Chinese balloons on two consecutive days during the Lunar New Year holiday last month, with some flying directly over the island.