Four foreign aid agencies have suspended work in a remote district of Nepal, saying two of their local staff were beaten by Maoist rebels.
Police detained students in the capital
The World Food Programme and UK, German and Dutch aid agencies said the rebels had also extorted money at a Maoist stronghold in western Kalikot district.
The news came as Nepal's army said it had rescued some 600 students seized by the Maoists in the west of the country.
In Kathmandu, police arrested at least 24 students at a pro-democracy rally.
In a statement on Sunday, the WFP, Britain's Department for International Development and the German GTZ and Dutch SNV aid agencies said their workers had been attacked in the village of Sukatiya, 600km (375 miles) west of Kathmandu.
"Maoist cadres seriously assaulted one male and one female staff member," the statement said.
"The female staff member was badly beaten. The Maoist cadres tried to force her to dig her grave, but she was too badly injured to do so. Both were forced to give money to the Maoists."
The rebels have not responded to the allegations. The pull-out will affect about 6,000 villagers working on a road project aided by the agencies.
Nepal, one of the world's poorest countries, relies heavily on international aid.
Meanwhile, an army statement said the hundreds of kidnapped students were rescued during an operation in a remote mountain village in the west of the country.
The king seized power in February
The army gave no further details.
In the past, students taken for what the rebels call indoctrination classes have been freed within in a few days.
Violence between the rebels, who want a republic, and the security forces has continued unabated since King Gyanendra seized power on 1 February.
More than 12,000 people have been killed in the conflict since it began in 1995.
The king has been criticised at home and abroad for eroding civil liberties.
On Sunday, police in the capital broke up a rally held by students who had defied a ban on demonstrations.
Students said that as well as the 24 arrests, five protesters had been injured in police baton charges.