The authorities are threatening tough reprisals against villagers who took police officers hostage during a violent confrontation over land.
State media reported that at least half of the estimated 30 police and other officials being held captive were released on Monday night.
Unconfirmed reports also suggested that an agreement had been reached for talks with local offficials and that the other captives would be released soon.
However, tension remains high, as security forces continue to seal off the restive district of Dong Tam in My Duc, southwest of Hanoi.
The deputy chief of Hanoi police, Bach Thanh Dinh, was quoted as saying that his priority was to rescue all of those still being held by angry villagers.
The violence flared on Saturday when police moved in to arrest four residents involved in a long simmering land dispute with the local authorities.
Villagers responded violently to the intrusion, driving out police squads with a hail of rocks and taking prisoner a number of officers and other officials.
Dinh was quoted by state media as saying that he would enforce the law and impose strict punishment on those responsible for the trouble.
He accused some of the protesters of escalating the confrontation and encouraging others to take illegal acts.
Local people have been enraged by local government plans to seize more than a hundred acres of farm land for the military owned telecom company, Viettel.
Like farmers in many districts across Vietnam they say the land they have worked for decades was suddenly seized by the authorities for development, with totally inadequate compensation offered in return.
Land in Vietnam is owned by the state but farmers often work plots assigned to their families generations ago and have no other means of livelihood.
Land activists and independent journalists say they have been kept away from the area by police roadblocks and that the villagers themselves have also sealed off entrances to the district.
One prominent land rights activists in Hanoi said he was detained for questioning by police for a number of hours and accused of helping to inspire the latest flare up.