“I hope this rare new experience can let the ‘new friend’ see a more complete democracy, freedom and pluralism of Taiwan,” Tsai posted to contributors “from across the Strait”, the strip of water separating the mainland and Taiwan. “Welcome to the world of Facebook!”

Beijing deems proudly democratic Taiwan a breakaway province to be taken back, by force if necessary, particularly if it makes moves towards formal independence.

Tsai is the leader of Taiwan’s opposition Democratic Progressive Party (DPP), which traditionally favours independence from the mainland and is expected to win presidential and parliamentary elections in January.

The surge in posts underscores how much attention is being paid to the island and its relationship with the mainland since a historic meeting between the two leaders at the weekend, the first since the Chinese civil war ended in 1949. State media praised the summit as a success on the road to unification.

The posts, many written in simplified Chinese characters used on the mainland, did not appear to be machine-generated spam or an attack, said DPP spokesman Cheng Yun-peng.

They seemed genuine, but the DPP had not verified their authenticity, he said.

One read: “...peaceful unification. One country, two systems. Break through the machinations and return to me Formosa”, referring to the island by its former name.

Chiang Kai-shek’s ruling Kuomintang fled to Taiwan after being defeated by the Communists in 1949. The island has been self-ruled since. Both sides agree there is “one China”, but disagree on the interpretation.

There were as many posts defending Tsai and the DPP, written in traditional Chinese characters used on the island. One said “online pen wars” may give writers from the mainland a sense of freedom.

“But when we take our presidential vote to the ballot box, you will wake up from your daydream because this is democracy – and you don’t have it,” it said.