Vietnam has released dissident Nguyen Ngoc Nhu Quynh from prison. She left the country immediately on a flight to the United States, said people with direct knowledge of the situation. Quynh, known as “Mother Mushroom,” is one of Vietnam's most famous dissidents. She was serving a 10-year prison sentence for spreading anti-government propaganda. One person with knowledge of her case told Reuters that Quynh was not alone. "She is flying with her children and mother," the person said. Vietnam's foreign ministry did not immediately answer a request for comment. The U.S. Embassy in Vietnam did not answer questions from the Reuters news agency. It told Reuters to contact the Vietnamese government. Quynh's mother could not be reached by telephone. News of the release came shortly after U.S. Defense Secretary Jim Mattis left Vietnam. It was not known if the release had any connection with his visit. Mattis arrived there on Tuesday and left for Singapore on Wednesday.