Taiwan has a right to engage with the world and no country can stop ⁠that, President Lai Ching-te told Eswatini's king after he arrived for a surprise trip that Taipei says Beijing tried to stop, as China condemned him as a "rat".

China views democratically governed Taiwan as part of its territory with no right to state-to-state ties, a position Taiwan's government strongly ⁠disputes, and Beijing has demanded countries stop any ​engagements ⁠with the island.

Last month, Taiwan said China had forced three Indian Ocean countries to pull overflight permission for Lai's aircraft to travel to the ⁠small southern African kingdom of Eswatini for the 40th anniversary of King Mswati III's ​accession. ⁠It is one of only 12 ‌countries with formal ties with Taipei.

"The Republic of China, Taiwan, is a sovereign nation and a Taiwan that belongs to the world," Lai told the king, ‌referring to Taiwan's official name, in comments provided by ‌the presidential office on Sunday.

"The 23 million people of Taiwan have the right to engage with the world, and no country has the right — nor should any country attempt — to prevent Taiwan from contributing ⁠to the world."

Lai arrived in the former Swaziland, home to around 1.3 million people, on Saturday, on a trip neither government had announced beforehand, having taken an Eswatini government aircraft.

The "arrive then announce" model is commonly used in high-level international diplomacy, minimising the "uncertain risks of potential interference from external forces", a senior Taiwan security official said, speaking on condition of anonymity due to the sensitivity of the issue.

Late Saturday, China's Taiwan Affairs Office ‌said Lai had "skulked" his way to Eswatini.

"Lai Ching-te's despicable conduct — like ​a rat scurrying across the street — will inevitably be met with ridicule ‌by the international community," a spokesperson said ⁠in a statement.

Taiwan's China-policy making Mainland Affairs Council said Lai did not ⁠need Beijing's permission to go anywhere.

"The Taiwan Affairs Office's fishwife's gutter talk is boring in the extreme," ‌it added.

Lai's cancelled plans ​last month due to the overflight problem ‌had prompted criticism of China from ​the U.S., and concern from the European Union, Britain, France and Germany.