The pro-democracy activist has been detained for "breaching bail conditions," a week after authorities released him. Police have again fired tear gas at protesters, including some calling on the US president for help.
Joshua Wong, a 22-year-old pro-democracy campaigner, announced on Sunday that he was detained by airport officials for violating bail terms.
"I believe the ridiculous circumstance I'm facing now is the direct consequence of the political prosecution and arrest [in Hong Kong]," Wong said in a Tweet on Sunday.
Wong was granted bail on August 30 after police arrested several activists.
Hong Kong police charged Wong with unlawfully organizing a public meeting outside police headquarters in June. The case has been adjourned until November 8.
Wong served two months in jail earlier this year over his role in the 2014 "Umbrella Movement" protests against a Beijing initiative to screen candidates for the city's top executive.
Read more: Hong Kong crisis — What you need to know
Last week, Wong traveled to Taiwan where he campaigned for democratic freedoms in Hong Kong with local politicians. He was arrested on Sunday morning on his way to Germany.
His tweets suggest that a procedural mistake had led to his arrest, as the court had previously approved overseas trips.
En route to Germany
Wong was released on bail Monday — around 24 hours after he was arrested — after a court confirmed his bail terms allowed for pre-planned travel and that his arrest was unfounded.
The activist confirmed that he was free again and ready to resume his travel to Germany where he had been invited to attend "a major event with politicians and business leaders in the German parliament."
'Liberate Hong Kong'
Meanwhile, pro-democracy protests continue in Hong Kong despite the city's Chief Executive Carrie Lam's decision to scrap a controversial extradition bill.
The bill, which sparked months of violent protests, would have allowed individuals from Hong Kong accused of having committed crimes in mainland China to be extradited and tried there.
On Sunday, thousands of demonstrators marched to the US consulate, urging President Donald Trump to "liberate" their city. Activists in Hong Kong demands more democratic freedoms in the semiautonomous Chinese territory.
Protesters — most of them clad in black shirts — chanted "Resist Beijing, Liberate Hong Kong" and "Stand with Hong Kong, fight for freedom," as they waved American flags. Some of them carried posters that read "President Trump, please liberate Hong Kong."
The 14-week-long protests have become the biggest challenge to Beijing's rule in Hong Kong since the city's return from Britain.
China's state-controlled media have portrayed the pro-democracy protests as an effort by foreign-backed "criminals" to split the territory from China.
Hong Kong Chief Executive Lam has pledged that the government would support an inquiry by the Hong Kong Independent Police Complaints Council into police brutality, which would be joined by overseas experts and two government appointees.
However, this falls short of the key demand from Hong Kong protesters that an independent inquiry, led by a judge, should be launched. Nearly 1,000 protesters have been arrested during the protests and many injured.
Lam also added that she would like to set up public dialogue, liaising with community leaders and academics.
"What happened in the last two months has shocked and saddened the Hong Kong people and made everyone upset about Hong Kong," she said.
However, Wong said the measure to withdraw the bill was "too little, too late." He called the move a "tactic" and urged the world not to be deceived by the Hong Kong and the Beijing governments. "They have conceded nothing in fact, and a full-scale clampdown is on the way."