A homemade bomb was hurled into the compound of an office of the United Nations in southwest Nepal but no one was injured and there was no damage, police and a UN official said on Saturday.
Unidentified people hurled the bomb over the gate of the office of a UN human rights agency in Nepalgunj, 320 km (200 miles) southwest of capital Kathmandu, late on Friday, said police official Mingma Lama.
No one was working in the office at the time, said Marty Logan, a UN spokesman in Kathmandu.
"There was no damage and no one was hurt," he said.
A little known group called 'Himali Tiger' had thrown pamphlets around the spot, but had not claimed responsibility, Lama said.
No one has been arrested, he said, and the motive of the attack was not immediately clear.
Nepal has only recently emerged from a decade-long civil war waged by Maoists, which killed more than 13,000 people.
Several armed groups are now fighting for regional autonomy.