A dissident Vietnamese blogger known by her pen name 'Mother Mushroom' has arrived in the United States after her surprise release from prison, telling a large crowd of supporters she will "never keep silent" in her fight for democracy in the one-party state. Nguyen Ngoc Nhu Quynh, 39, was quietly freed from a jail on Wednesday in Vietnam and put on a plane with her elderly mother and two young children who were seen smiling and hugging her in images shared on social media. Her unexpected release after two years behind bars came as US defence chief Jim Mattis visited Vietnam as part of warming ties between the former foes, who are eager to counter China's rising influence in Asia. Neither the Pentagon nor the Vietnamese government commented on the timing of Quynh's release, though the US embassy in Hanoi said they welcomed the move. The outspoken blogger, whose name comes from her daughter's nickname "mushroom", smiled and spoke to a large crowd of friends and supporters, many livestreaming the chaotic scene on Facebook, at Houston's George Bush airport where she arrived just before midnight on Wednesday. She said it was not an easy move leaving her country but vowed to "never keep silent" in her fight for rights issues back home. "I will continue to raise my voice until there is human rights in Vietnam, real human rights," she told AFP by phone before getting into a car with her family. Quynh has been behind bars since her arrest in 2016 when she was arrested while visiting a fellow activist in prison. She was later convicted for "anti-state propaganda" for publishing damning Facebook posts about deaths in police custody, a toxic spill in central Vietnam and the criticisms of the ruling communist party. She was sentenced to 10 years in jail last year, a heavy ruling that drew swift rebuke from the US, the EU and UN. Earlier this year police moved her to a prison hundreds of kilometres from her hometown Nha Trang in central Vietnam, which she said had taken a toll on her family who were exhausted by the travel. "It was time for me to think of my family, I made this final decision (to leave) for the future of my two kids," she said. - One out, one in - The US embassy in Hanoi said Quynh had requested to go to the US if released and urged Vietnam to free other activists. "We will continue to call on the government of Vietnam to immediately and unconditionally release all prisoners of conscience," embassy spokeswoman Karen Tang said. Her arrest grabbed headlines globally and she gained global fame after receiving the International Woman of Courage Award in 2017, presented to her in absentia by US First Lady Melania Trump. Her husband Donald Trump's administration has come under fire for not doing enough to protect human rights, especially in Vietnam. Though Vietnam has long jailed its critics, a hardline leadership in charge since 2016 has been accused of doubling down on efforts to silence activists. More than 55 bloggers, protesters and Facebookers have been jailed this year alone, according to an AFP tally, with the length and frequency of sentences steadily ticking upward. Soon after Quynh was released Wednesday, fellow dissident Nguyen Dinh Thanh, 27, was jailed for seven years for "spreading anti-state materials" in southern Binh Duong province. The former medical student was accused of printing 3,000 leaflets apparently to distribute at nationwide protests in June, according to state media. In another indication that Vietnam is not likely to let up its punishment of critics, activist Le Dinh Luong had his 20-year sentence upheld in an appeal trial Thursday in Nghe An province. The sentence is one of the harshest doled out to an activist in years.