Taiwan's President Tsai Ing-wen won a landslide election victory on Saturday as voters delivered a stunning rebuke of Beijing's campaign to isolate the self-ruled island and handed its first female leader a second term.

Tsai, 63, was greeted by thousands of jubilant flag-waving supporters outside her party headquarters, hailing a result which looks set to infuriate China.

"Today we have defended our democracy and freedom, tomorrow let us stand united to overcome all challenges and difficulties," she told the cheering crowd.

Official results showed Tsai secured 57 percent of the popular vote with a record-breaking 8.2 million ballots, 1.3 million more than her 2016 victory.

Her main rival Han Kuo-yu, from the China-friendly Kuomintang, racked up 39 percent and conceded defeat. The result is a blow for Beijing, which views Taiwan as its own territory and has made no secret of wanting to see Tsai turfed out. Over the last four years it ramped up economic, military and diplomatic pressure on the self-ruled island, hoping it would scare voters into supporting Tsai's opposition.

But the strong arm tactics backfired and voters flocked to her Democratic Progressive Party (DPP), fuelled in part by China's hardline response to months of huge and violent pro-democracy protests in Hong Kong.

The result was welcomed by the United States, Taiwan's primary military ally, with Secretary of State Mike Pompeo saluting Tsai's "commitment to maintaining cross-Strait stability in the face of unrelenting pressure".

Turnout in the poll was 75 percent, a jump of nearly 10 percent from Tsai's first presidential election victory four years ago. Official results showed the DPP managed to retain its majority in the island's unicameral parliament with 61 out of 113 seats, while the KMT took 38 seats.