Top Shia leaders announced their decision Tuesday after a meeting late Monday night in the city, an official said.
"Remember the Gujarat riots before voting for the Bharatiya Janata Party's prime ministerial candidate Narendra Modi. It's the RSS which is trying to make him a hero," Khoja Ashan Ashri Jamaat president Safdar Karmali said on behalf of various groups.
Karmali said the Muslim community "is not safe" under Modi and in order to foil the designs of the Rashtriya Swayamsevak Sangh (RSS), Muslims must vote for parties with secular credentials, which are the Congress and its allies.
Ali Akbar Sharoff, another prominent Shia leader, said that past differences of the community with the Congress and its leaders like Ahmed Patel must be buried now and Muslims should cast their votes in favour of that party.
Shia leader Shabbir Somji expressed concern that India was passing through a crucial phase with communal forces raising their heads and it was imperative for the minorities to strengthen the hands of the secular forces led by the Congress.
The development comes five days after a delegation of Shia leaders led by state Minority Affairs Minister Naseem Khan and senior community leader Irfan Kidwai met Chief Minister Prithviraj Chavan and expressed their full support to the Congress.
The meeting came soon after Lucknow-based Shia cleric Maulana Kalbe Jawwad met BJP president Rajnath Singh and expressed the community's support to the party.
The Shias have also rejected the so-called 'fatwa' (edict) issued by Maulana Jawwad, saying that as per the community's customs and traditions, 'fatwas' can only be issued from Iraq or Iran.
Hectic campaigning is also underway on various social networking websites, appealing to the country's 28 crore Muslims to vote en bloc for the Congress and defeat communal forces.
Some of the major groups that have expressed support to the Congress include the All India Shia Personal Law Board, the Mazare Shaeed Salis (Agra), the Mogha Masjid Imambada, the Imam of Shia Rehmatabad Masjid and Haideri Federation of India.