AHMEDABAD, India (AFP) - Indian police fired tear gas to break up clashes between Hindu and Muslim mobs in Mr Narendra Modi's heartland of Gujarat on the eve of his swearing-in as prime minister, officials said Monday.

Angry crowds set fire to several shops and vehicles and pelted stones at each other during the clashes in western Gujarat state's main city of Ahmedabad on Sunday night, police and fire officials said.

Ahmedabad joint police commissioner Manoj Shashidhar said officers fired tear gas to halt the violence which left four people injured.

Mr Shashidhar said an investigation was under way into the clashes which appear to have started when two cars from the different communities crashed in an accident during a marriage procession.

"The incident flared up following a petty argument between people of two communities on Sunday night in Gomtipur area of the city. The situation was immediately brought under control," Mr Shashidhar told AFP.

The incident escalated when mobs set property on fire, Ahmedabad chief fire officer M.S Dastur told AFP.

"Some three shops, one mini-bus and a couple of two wheelers were burnt during the incident," Mr Dastur said.

The clashes came as Hindu nationalist Modi, chief minister of Gujarat for 13 years, was set to be sworn as premier on Monday after a landslide victory at elections as head of the Bharatiya Janata Party.

Mr Modi has pledged national unity as he attempts to revive the faltering economy, but he remains tainted by anti-Muslim riots on his watch in Gujarat in 2002 that left at least 1,000 people, mainly Muslims, dead.

Mr Modi has denied wrongdoing and a court investigation found he has no case to answer.

But some members of religious minorities fear a rise in communal tensions under a Modi government and warn they will be sidelined at the expense of the Hindu majority.