Kashinath Tiwari of the royalist Hindu Youth Association was shot dead Saturday night by three unidentified attackers at Birgunj, about 160 km south of Katmandu.

Birgunj Police Chief Rajendraman Shrestha said four suspects have been arrested, and officers were questioning them over the attack.

Supporters of Tiwari's organization shut down the town and surrounding areas Sunday, blocking traffic and shuttering markets.

The town is an important trade gateway for Nepal, which imports much of its goods and oil from neighboring India.

Police said no one has claimed responsibility for killing Tiwari, whose group supported the restoration of the monarchy.

Former King Gyanendra was forced to step down from the centuries-old throne after a legislative vote declaring Nepal a republic, and the monarchy was abolished in the Himalayan nation in 2008.

Tiwari had led protests against the Maoists, the former communist rebels and opposition party, last month during a Maoist-imposed general strike to demand the ouster of the government. The Maoists had issued threats against Tiwari.