By Subir Bhaumik BBC reporter in Calcutta

Police in India's eastern state of Sikkim say they have arrested a top separatist leader from the neighbouring state of Assam.

Dhiren Boro, who heads the military wing of the outlawed National Democratic Front of Bodoland (NDFB) was arrested just past midnight from an apartment in Sikkim's capital, Gangtok.

Two bodyguards, his wife and two children, who were with him, were also detained.

The NDFB has been involved in a violent campaign for an independent Bodo homeland since it was established 10 years ago.

Sikkim police chief TN Tenzing told the BBC that a group of police commandos encircled the flat in which Dhiren Boro was staying with his family at least for the last six months.

Late-night raid

Just past midnight the policemen broke into the apartment and arrested the rebel leader and both his bodyguards.

Bodos make up 13% of Assam's population

Three assault rifles, several Chinese-made grenades and two wireless sets were recovered from the apartment.

Mr Tenzing said the police also took into custody Dhiren Boro's wife, Pratima Boro, and their two children.

However, the police chief said Mrs Boro may be released after questioning and kept in the rented apartment under police watch.

Anti-terror law

Mr Tenzing said Dhiren Boro would be booked under the Prevention of Terrorism Act, which came into existence in India late last year after much controversy.

This is the first time the law has been invoked in Sikkim, which is one of India's most peaceful states.

Police officials in the neighbouring state of West Bengal said that two NDFB rebels arrested by them last week near the Bhutan border had disclosed Dhiren Boro's location.

The rebel was staying in Tadong, on the outskirts of Gangtok, where locals knew him as a fruit merchant and a stockbroker.

The NDFB maintains several bases in southern Bhutan but some of their leaders have reportedly shifted into Sikkim and Nepal under pressure from the Bhutanese government in recent weeks.