A bomb exploded in front of Nepal's interim parliament in Kathmandu on Tuesday, creating panic and triggering intense police search.
However, there were no casualties, police said.
Security forces found pamphlets scattered in the New Baneshwor area, claiming the blast was the handiwork of a new organisation, Dynamic Youth Force.
Though the new budget session started on Monday, the house was not in session when the explosion occurred around 11.30 a.m.
However, Nepal's three major parties - the ruling Communist Party of Nepal-Unified Marxist Leninist and Nepali Congress as well as the opposition Maoist party - were holding a meeting inside to decide on the stalled process of drafting a new constitution.
None of the leaders were hurt.