Demonstrators choked roads, attacked police vehicles and also manhandled senior police officers who were at the spot to rein in the mob. Till reports last came in, a strong contingent, including columns of the Rapid Action force, was manning areas which were still smarting from tension.

The fire took place in the Kharezi madrasa in ward 22 of the Barasat municipality. Locals said the mosque is over 100 years old. Just before the early morning prayers, dissenters said, certain miscreants entered the madrasa and set it on fire. Local residents doused it, but by then several manuscripts and religious material had been burnt, they alleged.

Superintendent of Police, North 24 Parganas, Supratim Sarkar said: "It is difficult to say who is responsible for the fire but we have begun an inquiry. We must first keep the areas calm."

However, the news spread and so did the anger. Long stretches of Jessore Road and Taki Road were blocked in the morning. Later, Jamiat-Ulema-e-Hind leader Siddiqullah Chowdhury visited the spot, asking people to restrain themselves and at the same time demanding strict punishment for the guilty.

But by afternoon, the agitation had spilled over on the streets of Naupara, Amdanga, Madhyamgram, Basirhat, Beliaghata and Kahraibari. Protesters also tried to set fire to three police jeeps in Kadambachi. Sub-Divisional Police Officer of Barasat Mrinal Bhattacharya was also attacked.

Sources said the district administration might have got wind of the trouble in the morning, but reacted late. The agitators had become impatient by evening. The first police team reached Kadambachi More on Taki Road a little after 4 pm. It was the also the first to bear the brunt.

Agitators lobbed bricks and stones at the uniformed men, and the police, in turn, resorted to lathhicharge. They also fired two rounds in the air.