Shiv Sena and MNS activists, who are bitter political rivals, Thursday clashed outside the election office in the Mumbai collectorate.

Several thousands supporters of both parties had assembled for filing the nomination papers for Mumbai South Lok Sabha constituency by Shiv Sena candidate Arvind Sawant and Maharashra Navnirman Sena (MNS) candidate Aditya Shirodkar.

The MNS activists who were already present in large numbers started cheering their candidate and jeering at Shiv Sena workers.

Irked by this heckling and booing, the Shiv Sena activists also started raising anti-MNS slogans even as some workers both parties resorted to pushing around and punching each other.

Unconfirmed reports also said that stone-throwing took place.

Sensing trouble, the police immediately intervened and after a minor caning, brought the situation under control and detained at least 50 activists.

Shiv Sena leader Arvind Bhonsale later told mediapersons that the Election Commission authorities should not have given appointment to both parties' candidates on the same day.

MNS spokesperson Nitin Sardesai claimed that the rival workers attempted to prevent the nomination filing process from being completed smoothly.

A police official said that they have videographed the incident and after investigations, they would initiate necessary action against the culprits from both parties.

The two parties -- SS and MNS -- headed by warring cousins Uddhav Thackeray and Raj Thackeray respectively, have been at loggerheads for the past few weeks with both leaders criticizing each other publicly.