"Around 25-30 NCP activists swooped down on our party headquarters, shouting slogans against us. They grabbed a bundle of our banners and publicity material and made a bonfire of it," said AAP city treasurer Suresh Acharya.
He said that the angry NCP activists also smeared their party office hoardings with blank ink, tore down posters of AAP chief Arvind Kejriwal and left after a noisy demonstration.
There was no damage to AAP property or any human casualty, according to Acharya.
Acharya said that the immediate provocation for the attack could be AAP's ongoing campaign against senior NCP leader and state Deputy Chief Minister Ajit Pawar highlighting alleged corrupt activities in the power department handled by him.
"We are going to 'retaliate' in a peaceful manner this evening by sweeping the NCP Andheri west office with our brooms and praying to the Almighty to give them good sense not to indulge in such violence," he said.
Police who reached the AAP office soon afterwards managed to detain a few NCP activists and have now deployed more personnel to safeguard against similar future incidents.