The assailants, who came on two motorcycles, also smashed window panes of a vehicle parked in front of the office last night, they said.
The office - Walia Enterprises - belonged to Ballu Walia, the former block president of Bharatiya Janata Yuva Morcha, a frontal wing of BJP, they said.
While Walia was not present in the office at the time of the incident, Aman Basra, son of a Shiv Sena leader, who was there, was injured and had to be hospitalised, police said.
A case under the relevant sections of IPC, including 307 (attempt to murder), was registered against them, police said, adding efforts are on to nab the accused.