Taiwan's tourism sector suffered the worst summer in 13 years due to a slump in Chinese visitors, officials said Friday, as ties with Beijing deteriorate.

It was the island's weakest August performance since an outbreak of the killer respiratory disease SARS in 2003.

Taiwan saw a boom in mainland tourists under former Beijing-friendly president Ma Ying-jeou, with Chinese visitors accounting for about 40 percent of the total 10 million visitors in 2015.

But since Beijing-sceptic President Tsai Ing-wen was elected in January, relations have turned frosty and the number of Chinese tourists coming to Taiwan has dropped, with speculation Beijing is turning off the taps as a means of pressuring Tsai.

Taiwan is self-ruling but China still sees it as part of its territory.

Beijing wants Tsai to acknowledge there is only "one China", as did her predecessor Ma, paving the way for eight years of rapprochement and trade deals.

In August, the total number of tourists to Taiwan fell 3.4 percent to 863,540 from last year, despite a 30-40 percent increase in Japanese and Korean tourists, the Tourism Bureau said.

"It was the first monthly decrease this year and the first decrease for August peak summer time since 2003, when Taiwan's tourism was hit by a SARS outbreak," said Lynn Lin, deputy director of the bureau's planning division.

Chinese visitors fell 32.4 percent to around 248,600 from August 2015, including a nearly 55 percent decline in group tourists, according to the bureau.

Local tourism operators have said the industry is in crisis, with hotels only half-full and thousands of tour buses sitting idle.

Observers believe the decline is due to China limiting tour groups to Taiwan amid rapidly cooling relations under Tsai's government.

The island's tourism sector was also badly hit when a deadly bus crash in July killed an entire tour group from China's northeastern city of Dalian.

More than 10,000 tourism industry workers took to the streets of Taipei earlier this month to demand the government address their woes, including offering tax reductions, extending loan deadlines and reducing or waiving visa fees for Chinese tourists.

The cabinet has announced Tw$30 billion ($955 million)in loans to the tourism industry, although it has denied it is a "rescue package" to offset the Chinese tourist slump, instead framing it as helping the industry upgrade.