* Prominent HK democracy activist Wong among three arrested
* Wong pushed into car on the street, says his party
* Protesters cancel banned march planned for Saturday
* Amnesty says 'climate of fear' in Hong Kong (Recasts)
HONG KONG, Aug 30 (Reuters) - Hong Kong authorities on Friday charged pro-democracy activist Joshua Wong with organising an illegal protest as they tighten a clampdown on unrest that has plunged the Asian financial hub into its biggest political crisis in more than two decades.
Wong, who led pro-democracy demonstrations five years ago that foreshadowed the latest turbulence, is the most prominent activist to be arrested since protests escalated in mid-June over fears China was exerting greater control over the city.
Police arrested several other activists and blocked plans for a mass demonstration on Saturday, in a show of force a day before the fifth anniversary of China's decision to rule out universal suffrage in the former British colony.
The bespectacled Wong, who was 17 when he became the face of the student-led Umbrella Movement, has not been a prominent figure in current protests, which have no identifiable leaders.
He was released from jail in June after serving a five-week term for contempt of court.
Wong and fellow activist Agnes Chow were charged with unlawfully organising a public meeting outside police headquarters on June 21. They were released on bail and the case was adjourned until Nov. 8.
Thousands of demonstrators blockaded police headquarters on June 21 protesting a now-suspended extradition bill that would have allowed people to be sent to mainland China for trial in Communist Party-controlled courts.
Andy Chan, a founder of the pro-independence Hong Kong National Party that was banned last September, was arrested at Hong Kong's international airport on Thursday on suspicion of participating in riots and attacking police, police said.
Wong's pro-democracy group, Demosisto, said the arrests were an attempt to scapegoat individuals in a movement that has built momentum without public figureheads.
"The arrests were apparently a political operation," Demosisto said on its Facebook page. "It will only make the government misjudge the public, leading to a deadly situation that is more difficult to resolve."
The Civil Human Rights Front, the organiser of previous protests, cancelled a mass demonstration planned for Saturday after the police refused permission.
More than three months of unrest sparked by anger over the extradition bill has evolved into calls for greater democracy under the "one country, two systems" formula, under which Hong Kong has been ruled since 1997, guaranteeing freedoms not enjoyed on the mainland.
Protesters are riled by perceived interference by China that undermines the "one country, two systems" arrangement.
Reuters exclusively reported on Friday that Chief Executive Carrie Lam previously requested Beijing's approval for a plan to ease tension, evidence of the extent to which China is controlling the Hong Kong government's response to the unrest.
"CLIMATE OF FEAR"
Nearly 900 people have been arrested since the demonstrations began with frequent clashes between protesters and police, who have at times fired tear gas and rubber bullets to disperse activists.
With protesters and authorities locked in impasse, as Hong Kong faces its first recession in a decade, speculation has grown that the government may impose emergency law, giving it extra powers over detentions, censorship and curfews.
The government would consider using "all laws" to prevent violence, Hong Kong leader Lam, who has become a lightning rod for protesters' anger, said this week.
Hong Kong was a long way from having to make use of emergency powers, a senior official of China's parliament told Reuters on Friday.
China has accused foreign powers, particularly the United States and Britain, of fomenting the demonstrations in Hong Kong and warned against foreign governments interfering in the protests.
A photograph in a pro-Beijing newspaper this month of Wong meeting a U.S. consular official triggered a war of words between Washington and Beijing.
China brought fresh troops into Hong Kong on Thursday in what it called a routine rotation of its garrison there.
Chinese state media stressed the troop movement was routine and Asian and Western diplomats watching the People's Liberation Army (PLA) forces in the territory had been expecting it.
On its Facebook page, the Civil Human Rights Front said its leader, Jimmy Sham, was attacked by two men armed with a knife and a baseball bat on Thursday. He was not hurt but a friend who tried to protect him was injured.
"The repeated harassment of pro-democracy activists, combined with police bans on demonstrations, has created a climate of fear for peaceful protesters," rights group Amnesty International said in a statement. (Reporting by Jessie Pang, Donny Kwok, Twinnie Siu, Felix Tam, Ryan Chang, Joyce Zhou and Anne Marie Roantree; writing by Joe Brock; Editing by Paul Tait and Clarence Fernandez)