Police in Nepal said Wednesday they had detained 12 people accused of illegally sending young men to be recruited into the Russian army, days after authorities confirmed the death of six Nepalis fighting for Moscow.

Nepal prohibits its citizens from joining foreign armies, except those of countries with which it has agreements to do so.

Those detained had allegedly procured documents and arranged visas to send people to Russia via India and the United Arab Emirates, according to Nepal district police spokesman Kumud Dhungel.

"They were then recruited in the army," he told AFP. "It is unclear right now how many people were sent this way but an investigation is underway."

Dhungel said that those sent to Russia were charged up to $8,500 each by the brokers.

Nepal said Monday that six citizens had been killed while serving as mercenaries in the Russian army and another had been captured in Ukraine.

The announcement did not specify where, how or when the six were killed.

Kathmandu urged Moscow to stop the use of Nepali mercenaries and send any men serving back home. 

The statement follows an official government warning in August urging Nepalis not to engage in security-related work in war-torn countries. 

It came as Russian troops were trying to seize Avdiivka, an industrial town in the eastern Donetsk region of Ukraine that has become one of the most contested points on the frontline. 

Nepal is over 5,350 kilometres (3,325 miles) from the bloodshed in Ukraine sparked by Russia's invasion.

Many Nepalis go abroad to earn money and remittances are crucial for Nepal's economy, equalling nearly a quarter of GDP last year according to the World Bank. 

Nepal's Gurkhas have long been recruited into the British army, earning a reputation for fierce fighting and bravery since they first served as troops in then-British-ruled India in 1815.