Malaysian immigration authorities on Tuesday denied entry to Hong Kong student activist Joshua Wong, who had been invited to the Southeast Asian nation to participate in academic talks on democracy in China and last year's protests in Hong Kong.
Wong was one of the main leaders of the Hong Kong protests, which shut down key roads in the city for 79 days and presented China's Communist Party leadership with one of its biggest political challenges in decades.
Online news portal Malaysiakini said Wong was detained soon after arriving at the airport on the northern island of Penang on Tuesday morning, and then put on a plane back to Hong Kong.
"Malaysia's government doesn't allow me to enter, now on my way back to Hong Kong," Wong posted in Mandarin on his Facebook page at about 0500 GMT.
A Malaysian immigration official had said it was a "government order" to deny him entry, Wong wrote.
Penang immigration authorities declined immediate comment, when contacted by Reuters.
Malaysiakini reported that Home Minister Ahmad Zahid Hamidi said he had no knowledge the 18-year-old had been denied entry to Malaysia.
Wong was dragged away by immigration officers, and was heard shouting, "Don't use violence," Malaysiakini added.
Wong's Facebook page showed he had been invited to participate in a series of seminars in the cities of Ipoh, Johor Bahru, and the capital, Kuala Lumpur, besides Penang.
Human rights activist Ng Yap-hwa, an organizer of the event at which Wong had been invited to speak, said he was angry at Wong's treatment.
"We are still demanding that the government make clear why they stopped Joshua Wong from coming here," he said.
"We're angry at the government's actions because there's no reason that the Malaysian government should stop us from organizing any international talk on the democracy movement."
In 2013, Malaysian authorities deported Australian senator Nick Xenophon after refusing him entry over his participation in an illegal street rally for electoral reforms in 2012, saying that he was considered a "security risk".