In a blog post, Hong Kong Financial Secretary Paul Chan said visitor numbers fell almost 40% from last year.

That marked a sharp deepening of the 5% year-on-year decline in July, he said.

Last year, Hong Kong was one of the world's most visited cities, with 30 million tourists.

The city has faced months of protests that still show no signs of ending.

The demonstrations began over a proposed extradition bill between the territory and mainland China, and have evolved into demands for greater freedoms.

Hong Kong is part of China, but its citizens have more autonomy than those on the mainland.

Clashes between police and activists have become increasingly violent, with police using tear gas and protesters storming parliament.

The unrest has dealt a blow to the territory's economy, specifically its tourism and retail sectors.

In August, protesters paralysed the airport for several days. Hundreds of flights had to be cancelled.

Image copyright Getty Images

Image caption Protesters fill the arrival hall at Hong Kong International Airport on 12 August

Mr Chan said in some areas, hotel occupancy rates in August fell by more than half, and house prices sank by as much as 70%.

"The retail and even the catering industry are similar. The most worrying thing is that the road ahead does not seem to be easy to get better," he said in a translation of the blog posted on Sunday.

The finance chief said the demonstrations have "severely damaged Hong Kong's international image" as a safe city for trade, aviation and finance.

Some economists forecast the hit from the protests, coupled with the impact of US-China trade war, will push Hong Kong's economy into a technical recession later this year.

The shifting political landscape has also complicated the environment for many businesses in Hong Kong.

Cathay Pacific became embroiled in controversy over its response to demonstrations, with two executives including former boss Rupert Hogg quitting over the affair.