(Reuters) - Hong Kong activists urged Taiwan on Tuesday to help promote democracy in the Chinese-ruled city amid its worst political crisis in decades and called for a mass rally before the 70th anniversary of the founding of Communist China on Oct. 1.

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Hundreds of thousands of people have taken to the streets of Hong Kong since mid-June in sometimes violent protests denouncing perceived creeping interference by Beijing. China denies the charge.

Hong Kong, a former British colony, returned to Chinese rule in 1997 under a “one country, two systems” formula guaranteeing its freedoms. China has suggested the same formula for Taiwan, which it considers an unruly, breakaway province.

Many in Taiwan have been closely watching Hong Kong and become increasingly wary of Beijing’s “reunification” agenda.

“I hope people can brainstorm together on how to win this war against Beijing’s white terror and authoritarian rule,” Lester Shum, one of the student leaders of Hong Kong’s pro-democracy “Umbrella” movement five years ago that foreshadowed the current unrest, told reporters in Taipei.

White terror is a common expression to describe anonymous acts that create a climate of fear.

“Friends in Taiwan are not bystanders of the movement inHong Kong. Taiwanese are participants,” he said. “China will definitely want to take over Taiwan after it takes over Hong Kong.”

Joshua Wong, one of the most visible leaders of the 2014movement, called for a mass rally.

“We hope Hong Kong can one day become Taiwan, a place with democracy and freedom,” he said.

Wong is on bail after he was arrested last week, charged with inciting and participating in an unauthorized assembly outside Hong Kong police headquarters on June 21.

Taiwan President Tsai Ing-wen said on Tuesday her administration was keeping a close eye on the Hong Kong crisis.

Beijing has accused Taipei of supporting the Hong Kong protests, an accusation Taiwan denies.

“Like the rest of the international community, when necessary and based on humanitarian concerns, we will provide necessary assistance to Hong Kong residents in Taiwan, and will not just stand on the sidelines and watch,” she said in a statement.

“The Republic of China (Taiwan) staunchly supports democracy and freedom in Hong Kong, and hopes that Hong Kong society can quickly restore stability.”

Hong Kong pro-democracy lawmaker Eddie Chu urged Taiwan authorities to come up with “humanitarian mechanism” to take in demonstrators from the city, after hundreds of arrests since the protests began.

“There could be even worse conflict to come in Hong Kong...We hope the Taiwan government and political parties can make preparations for that scenario,” he said.