Here is a 10-point cheat sheet to this story:
Clashes broke out between the two groups in Raniganj, a town in the coal belt, when some shops were set on fire while the Ram Navami procession was passing through the area. One villager was killed and three police officers were injured in the violence. Motorcycles were set on fire and policemen were attacked at a local market.
"Asansol-Durgapur Deputy Commissioner of Police Arindam Dutta Chowdhury was injured in the incident. He lost a hand when the agitators hurled a bomb at him. He has been admitted to a private hospital," a police officer said.
Union minister and BJP's MP from Asansol Babul Supriyo, who was supposed to participate in one of the rallies in Raniganj but backed out at the last moment, alleged that it was a "premeditated attack, meant to hurt me".
In Murshidabad's Kandi, an armed crowd barged into a police station, at which the police had to retaliate. Batons were used to control the situation. Visuals from the area showed frenzied mobs rushing around, their faces smeared with red. Clashes were also reported from Bardhaman, where a puja pandal was attacked.
On Sunday, one person was killed and five policemen were injured in clashes during a procession in Purulia, as sword-wielding BJP supporters defied a government ban on armed rallies at several places in West Bengal, police said.
A furious Mamata Banerjee warned of strong action against those involved in violence. "Some unidentified people have come here from outside...These trouble-mongers holding pistols and swords are resorting to hooliganism. This is West Bengal. This is not our culture. We celebrate Durga Puja, Kali Puja, Ganpati puja peacefully. We also celebrate Ramzan, Christmas," she said.
Ram Navami has never been a major festival in Bengal but over the last two years, the BJP has been especially active, holding rallies where participants are often armed with traditional weapons like swords and tridents. This year, the ruling Trinamool also joined the BJP in celebrating the festival.
State BJP president Dilip Ghosh participated in one of the rallies in West Midnapore, armed with a sword. So did the party's women wing president Locket Chatterjee and national secretary Rahul Sinha. "We are celebrating this festival for years, no one should resist us. It is the government's duty to maintain the peace. Our groups have got permission to celebrate, this is a religious festival," Dilip Ghosh had said.
A case was today registered against Locket Chatterjee for allegedly participating in an armed Ram Navami procession in Birbhum district yesterday, police said.
In state capital Kolkata, more than 60 rallies were organised - some of them by the ruling Trinamool Congress and led by the party's senior leaders like Firhad Hakim and Sadhan Pande. But most of the violence have centred around armed rallies - in many cases held without police permission despite a stern warning from the state government.