More than 30 Chinese military aircraft were detected around Taiwan in a 24-hour window, Taipei's defence ministry said Saturday, marking the largest show of force around the island since it held crucial elections.

China claims Taiwan as part of its territory, and has never renounced the use of force to try to bring the self-ruled island under its control.

Ahead of Taiwan's January 13 poll, Beijing warned voters that presidential candidate Lai Ching-te -- the current vice president whom China has called a "dangerous separatist" -- would bring "war and decline" if chosen to lead.

Lai still won the election, securing an unprecedented third term for the Democratic Progressive Party, which has long rejected China's territorial claim on Taiwan.

In the 24 hours leading up to 6:00 am Saturday (2200 GMT Friday), the Ministry of National Defence detected 33 Chinese military aircraft and seven naval ships operating around Taiwan, it said in a statement.

Thirteen of the aircraft "crossed the median line of the Taiwan Strait", it said.

Taiwan's armed forces have "monitored the situation and employed (air patrol) aircraft, Navy vessels, and coastal missile systems in response to the detected activities".

Two Chinese balloons were also detected crossing the sensitive Taiwan Strait, which separates China from the island.

The show of force also came after a visit by two US lawmakers to Taipei to meet president-elect Lai and his running mate Hsiao Bi-khim -- criticised by Beijing as an "independence duo".

Lai has in the past been outspoken about the issue -- a red line for China -- calling himself a "pragmatic worker of Taiwan independence".

But he has moderated his stance and vowed to follow President Tsai Ing-wen's path of maintaining the status quo while bolstering the island's defence capabilities.

Two days after his election, Pacific nation Nauru announced it was switching its diplomatic relations from Taipei to Beijing -- reducing Taiwan's already short list of allies to twelve.

One of them, Tuvalu, is now being closely watched, as its pro-Taiwan prime minister just lost his parliamentary seat, according to election results released Saturday.