Kathmandu: About 500 Nepalese riot police who revolted and took their senior officers hostage to protest poor working conditions released their captives and surrendered after a two-day standoff, officials said on Monday.

Seven senior police officers were released unharmed just after midnight on Sunday, said Narendra Sharma, chief government administrator in the area.

The armed policemen took over a riot police camp on Saturday at Nepalgunj, about 500 kilometres west of Kathmandu.

They were protesting the alleged ill-treatment of lower-ranking officers by their supervisors, low-quality food and other issues.

Police threw a thick cordon around the camp on Sunday after the government ordered an immediate end to the standoff, Sharma said.

"The revolting policemen allowed their hostages to leave after midnight and they are all being held at the police training camp," Sharma said.

There had been reports of shots fired during the standoff, but no one was believed to have been hurt.

Home Secretary Umesh Mainali said authorities were assessing how to improve the 68,000-member force after two revolts in a month.

"We are reviewing to find out what changes are needed to be made in the police force and how to ensure that discipline is strictly maintained," Mainali said.

Four men in handcuffs were shown to reporters, including the alleged leader of the insurrection.