A blast in an office in a suburb of Kathmandu wounded two guards, police said on Wednesday, blaming it on Maoist rebels who have stepped up attacks across the Kingdom.
A police officer said the explosion took place on Tuesday night at the office of the King Mahendra Trust for Nature Conservation, an environmental group headed by Nepal's Crown Prince Paras.
"It has caused minor property damage," the police officer said.
At least 33 people were killed on Tuesday in clashes between security forces and Maoists that followed the end of a rebel-led blockade.
The rebels are trying to topple the impoverished country's monarchy and set up a communist republic in a conflict that has killed more than 13,000 people over the past decade.
King Gyanendra seized power last year, justifying it as necessary in the fight against the insurgents.