Her younger brother, Liu Hui, was not on the plane, they said.
While authorities allowed Liu Xia to leave China, her brother Liu Hui reportedly has remained in China. "We hope she is en route to freedom and hopefully a more peaceful life".
China on Tuesday allowed Liu Xia to fly to Berlin, ending an eight-year house arrest that drew worldwide criticism and made the soft-spoken, chain-smoking 57-year-old poet with a shaven head a tragic icon known around the world.More news: George Clooney injured in bike crash
"Now, the harassment of Liu Xia's family who remain in China must end too".
China sentenced Liu Xiaobo in December 2009 to 11 years imprisonment on charges of inciting subversion of state power after he helped write a manifesto calling for political and economic liberalization.
Last year, she appeared pale, gaunt and somber in images released by the authorities as she cared for Liu Xiaobo just before his death from liver cancer in a hospital under police custody.
The move comes a day after Chinese premier Li Keqiang met German Chancellor Angela Merkel.
While precise details of Liu's flight out of China are unknown, the only Finnair flight that left Beijing Capital International Airport bound for Berlin on Tuesday morning was Flight AY86, which took off at 10.55am, according to the airport's website. "Only by taking medication can I fall asleep and stop looking at this painful world", she said, according to Ye. The country has been raising human rights issues and the situation of Liu Xia on multiple occasions with China, a major trade partner and investor. "We call on the worldwide community to continue to try to save Liu Hui, to release Liu Xia from worries, to let her obtain true freedom". In April, she said to a friend in an emotional phone call, "If I can't leave, I'll die in my home..."More news: YouTube spends $25 million to fight fake news
Liu Xia poses with a photo of her and her husband during an interview at her home in Beijing on December 6, 2012. Throughout his hospitalization, authorities closely guarded Liu and only once allowed two independent foreign doctors to have access to Liu a week before his death.
Johnny Lau, a political commentator in Hong Kong, said he believed the authorities had let Liu Xia go to avoid her case sparking a "surge" of pressure on China around the July 13 anniversary of Liu Xiaobo's death.
Liu Xiaobo was only the second Nobel Peace Prize victor to die in police custody, and human rights group say that shows the Communist Party's increasingly hard line.
In May, dozens of the world's leading writers and artists, from Michael Chabon to Paul Auster and Khaled Hosseini, called on China to release her to seek medical treatment overseas.
Western diplomats and rights groups had earlier hoped to be able to get Liu Hui out of China as well.More news: Brazil star Neymar urge PSG to sign Suarez from Barcelona this summer
- Arsenal complete move for Sampdoria midfielder Lucas Torreira
- OnePlus 6 256GB Midnight Black now available in India
- UK's May names new foreign secretary
- West Ham signs Wilshere from Arsenal
- Netflix Debuts "Smart Download" Feature As Boost For Binges
- Suspects Pummel 92-Year-Old Man with Brick in Southern Los Angeles
- Tories rally behind PM amid Brexit chaos - but should May stay?
- Cristiano Ronaldo: Juventus set to sign Real Madrid forward
- Pick your England XI for Croatia semi-final
- One dead in Pretoria charter plane crash