Around 40 activists of Hindu Raksha Dal broke flower pots kept outside the AAP's office and tore party posters. Some glass doors were also smashed in the attack.
"We today staged a protest against AAP's stand on Kashmir. AAP leader Prashant Bhushan's remark on Kashmir are very sad for Hindus due to which we staged a protest outside the party office," said Pinky Choudhary, national convenor, Hindu Raksha Dal.
SSP Dharmendra Singh said, "We have identified some people. They were some residents of Ghaziabad and the numbers of their cars have been noted. Action against them will be initiated soon."
AAP spokesperson Dilip Pandey said, "Some youths, who are said to belong to Hindu Raksha Dal, gathered outside the party office and raised slogans against AAP. They also broke flower pots placed outside the party office".
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Police have registered a case against unknown persons.
The SSP said there was no security at the party office but policemen have now been deployed there and at Delhi Chief Minister Arvind Kejriwal's residence which is just a kilometre away.
Bhushan had recently said a referendum should be carried out in Kashmir to decide on deployment of the army to deal with security threats in the Valley.
However, the Aam Aadmi Party had distanced itself from his views.