China hopes self-ruled Taiwan's only remaining African ally, Swaziland, will sever ties with Taipei before China hosts a summit of African leaders this year, the foreign ministry said on Friday, keeping up the pressure on Taiwan.

Taiwan is claimed by China as its own, with Beijing saying that as it is merely a Chinese province it has no right to state-to-state relations.

Taiwan has lost two diplomatic allies in the past month, most recently the West African state of Burkina Faso, which re-established ties with Beijing last weekend. The Chinese government's top diplomat State Councillor Wang Yi urged Swaziland to follow suit.

Taiwan says it has received assurances from Swaziland that ties are secure and that it expected Swaziland's King Mswati III, who is Africa's last absolute monarch, to visit soon.

Speaking at a daily news briefing in Beijing, Chinese Foreign Ministry spokesperson Hua Chunying said their door was open to Swaziland.

"We of course welcome Swaziland to join the family of China-Africa cooperation at an early date, and hope that by the time the China-Africa cooperation forum Beijing summit happens, we can have a happy picture of the whole family," she said.

"Of course this hinges upon Swaziland's own decision."

China will host the summit, where Chinese leaders typically dole out large loan packages for the continent, in Beijing in early September.

Taiwan has official relations with just 18 countries worldwide, many of them poor nations in Central America and the Pacific such as Belize and Nauru.

Taiwan has accused China of using dollar diplomacy to lure away its allies, promising generous aid packages, charges China has denied.

Taiwan President Tsai Ing-wen visited Swaziland in April to shore up ties.

China has mounted a concerted campaign over the past two years to lure away Taiwan's remaining diplomatic allies, as it seeks to pressure Tsai, who it fears wants to push for the island's formal independence.

Tsai says she wants to maintain the status quo but will not be bullied by China and will defend Taiwan and its democracy.