A crude bomb was hurled at the BJP office in Thiruvananthapuram, but there was no casualty, police said on Wednesday.
The incident occurred at around midnight.
Glass panes of the main entrance door were damaged in the incident, Thiruvananthapuram city police commissioner, S Sparjan Kumar told PTI.
There were three to four BJP workers on the top floor of the office when the crude bomb was hurled, but none were injured.
Party sources said the bomb exploded hardly 45 minutes after state BJP President Kummanam Rajasekharan left the office.
To protest over the incident, BJP would take out a march to the Secretariat in the district.