Shouting slogans like "Marathis Go Back", the alleged activists of Rashtravadi Shiv Sena broke flower pots, glass doors and window panes of the Maharashtra Sadan at around 12:30 p.m.

Fooling security guards by entering the building in small groups, the attackers suddenly started damaging the property near the reception counter.

The protestors also raised slogans against Maharashtra government and Thackeray.

"They came inside the building in small groups. Nobody has any clue. They suddenly started shouting slogans and indulged in violence," Pramod Kolate, an official of the Sadan who was at the reception, said.

Resident Commissioner Apurva Chandra has already apprised Maharashtra Chief Minister Vilasrao Deshmukh and Deputy Chief Minister R R Patil about the incident besides lodging a complaint with police.

Sources said the Maharashtra government is approaching Union Home Ministry and Delhi Police for enhancing the security of the building.

During Diwali, sources claimed, security was enhanced at the building but was withdrawn later.

Shiv Sena MP Sanjay Raut, who visited the Sadan after the attack, termed the incident an "attack on Maharashtra".