Kathmandu - A bomb went off in a busy government office in south-eastern Nepal on Wednesday, wounding at least eight people, police said.

The bomb targeted land revenue office in the regional town of Janakpur, about 250 kilometres south-east of the Nepalese capital Kathmandu, at a time when the office was crowded with people.

The police said the blast was caused by an improvised explosive device that was hurled at the office by two men on a motorcycle.

Three of the injured, including a government employee, were in serious condition, the police said.

A rebel group calling itself Janatantrik Terai Mukti Morcha (JTTM) claimed responsibility for the attack.

Police said they were investigating the incident.

The attack came despite a government invitation to rebel groups in southern Nepal to hold a dialogue to end violence.

There are about two dozen armed groups operating in southern Nepal which the government says is involved in murder, abduction and extortion.

Only a few rebel groups have formally accepted the government offer of talks and there has been no let up in violence across the southern plains known as Terai.

Last week similar explosion killed three people in Chandranighapur near Janakpur. (dpa)