Supporters of each candidate gathered in Taipei, the capital, and Kaohsiung, where Han is mayor, to await the official outcome.

The self-governing island is expected to know later Saturday whether Tsai triumphed with her tough stance toward China.

The mood at Tsai's Democratic Progressive Party headquarters was festive, with supporters cheering as numbers were updated.

Taiwan has developed its own identity since separating from China during civil war in 1949 but has never declared formal independence. Beijing still claims sovereignty over the island of 23 million people and threatens to use force to seize control if necessary.

Han voted in Kaohsiung, where he is mayor. A third-party candidate, James Soong, also ran but had virtually no chance of winning.

For many in Taiwan, months of anti-government protests in Hong Kong, a semi-autonomous Chinese territory, have driven home the contrast between their democratically-governed island and authoritarian, communist-ruled mainland China.

Tsai portrayed the election as a chance to protect Taiwan's democracy.

"Let us tell the world with our own votes that Taiwanese are determined to defend sovereignty, determined to guard democracy and determined to persist in reforms," she said at a rally late Friday.

The Nationalist Party's Han has said Taiwan should be more open to negotiations with China, in contrast to Tsai, who has dismissed Beijing's overtures.

The Hong Kong protests have undermined support in Taiwan for the "one country, two systems" approach Beijing has championed for governing both that former British colony and Taiwan.

Fears of Chinese interference in Taiwan's politics and an uptick in the economy helped Tsai regain an edge after a dire electoral setback for her Democratic Progressive Party, or DPP, 14 months ago.

"The reason why I vote for her is for upholding the value of Taiwan's freedom and democracy and that should not be affected by the other side of the strait (China)," Lucy Ting, a college student, said at Tsai's rally.

The Nationalists have struggled to find candidates who can fire up their pro-China supporters and win over young Taiwanese who increasingly favour the DPP.

A second term for Tsai is expected to draw more diplomatic, economic and military pressure from Beijing on the island, in a continuation of Chinese President Xi Jinping's campaign to compel her administration to endorse its insistence that Taiwan is a part of China.

Tsai has refused to do so, maintaining that Beijing has no claim over Taiwan, although her government has repeatedly called for the reopening of talks between the sides without preconditions.

Australian Associated Press