The Aam Aadmi Party (AAP) office at Kaushambi, in neighbouring Ghaziabad, was attacked on Wednesday by workers of a fringe Hindu group - Hindu Raksha Dal - who were protesting party leader Prashant Bhushan's remarks on Kashmir.

A mob of about 50-60 workers pelted stones at AAP's Kaushambi office around 11.00am.

Bhupender Tomar spokesperson of the Hindu Raksha Dal's Ghaziabad wing said that the act was carried out to oppose Bhushan's statement over Kashmir and insisted that Kashmir is an inseparable part of India.

"When Prashant Bhushan had said this earlier, I had beaten him up in his chamber as well. We can't tolerate this," said Vishnu Gupta, an activist of the Hindu Raksha Dal.

Bhushan had said that a referendum should be carried out in Kashmir before deployment of the army to deal with internal security threats in the Valley.

In a statement on Monday, Bhushan had said that he believed Kashmir is an integral part of India.

"Any reference to referendum should not be misconstrued to mean plebiscite on Kashmir's relationship with India," Bhushan said.

In 2011, Bhushan supported a plebiscite in Kashmir and told a TV channel that a referendum should be carried out in Kashmir to decide on deployment of the army in the Valley.

The AAP office at Kaushambi is located not far from the residence of AAP convenor and Delhi chief minister Arvind Kejriwal. The incident also raises questions over Kejriwal's decision to deny security cover.

They barged into the AAP office, stoned it heavily shattering windows, broke flower pots and abused AAP leaders, said AAP leader Dilip Pandey.

Pandey said they were from a group called Hindu Raksha Dal.

"All our volunteers were asked to get inside (the office) when the attack took place," Pandey said, adding the attackers raised slogans against a particular community.

The attackers, in their 20s and 30s, came in four or five cars. Before fleeing after some 20 minutes, the attackers threatened to attack AAP leaders in the future too.

"They had lathis and threw bricks at us. Fortunately our door was closed, otherwise many would have been injured," said an AAP volunteer.