Student leaders of Hong Kong's pro-democracy Umbrella Movement said Sunday they would seek closer ties with Taiwan after the island elected a new president who pledged to stand up to China.

Tsai Ing-wen of Taiwan's main opposition party won by a landslide Saturday as voters expressed their discontent over warmer relations with China under the ruling Kuomintang (KMT).

"Whether it is the issue of Taiwan's sovereignty or the future of Hong Kong, we both face the China factor," said Joshua Wong, the teenage face of the Umbrella Movement which brought parts of Hong Kong to a standstill in 2014 seeking fully free leadership elections.

"I think more exchange is very much needed," Wong told a press conference in Taipei.

The 19-year-old was in Taiwan as part of a pro-democracy group observing Saturday's elections.

Hong Kong is semi-autonomous since being returned to China by Britain in 1997 and enjoys freedoms unseen on the mainland, but there are fears those freedoms are being lost.

The pro-democracy rallies in Hong Kong were sparked when Beijing insisted on vetting candidates for the city's next leader.

Self-ruling Taiwan split from China in 1949 after a civil war on the mainland. But Beijing still sees it as part of its territory awaiting reunification, by force if necessary.

The KMT's Beijing-friendly strategy brought trade deals and a tourist boom but sparked fears that China was trying to erode Taiwan's autonomy through economic ties.

Support for Tsai surged as Taiwanese sought to assert their own identity and reject China's influence.

The island saw its own mass protests in 2014 when student-led demonstrators occupied parliament over a trade pact with China, in what became known as the Sunflower Movement.

"We face the same threat, we have to guard our places, to own our destiny. We need to have stronger alliances in all areas," said Alex Chow, another key Umbrella leader speaking in Taipei Sunday.

He called for more dialogue, whether through civil groups or the new government.

The calls for unity come in the wake of the disappearance of five Hong Kong booksellers from a publishing house known for titles critical of the Chinese government -- the latest incident to exacerbate fears over the city's autonomy.

Sunflower activists gained seats in Taiwan's legislature in Saturday's parliamentary vote, standing for the New Power Party (NPP) which grew out of the protest movement.

In Hong Kong, former Umbrella protesters also took seats in recent district elections.

Wong said the NPP was an inspiration.

"How they can turn street protests to power within the legislative system, I think that can serve as a very good reference for those in post-Umbrella student or civil movements in Hong Kong," he said.