Some “30 to 50” BJP youth activists, shouting “Jai Shri Ram”, descended on the state Congress headquarters in Entally on Saturday morning, bruised the septuagenarian liftman-cum-caretaker with a stick and defaced the boundary wall.

Abdul Jabbar, 70, “Chacha” to party officials and visitors, said he had locked the main gate of Bidhan Bhavan as soon as he saw the mob but one of the youths hurled a bamboo stick over the gate, hitting him in the head.

“They came around 11.30am. They got angry because they couldn’t enter the premises and threw the stick. I could have been seriously injured,” Jabbar, who lives inside the premises, said.

Some 20 to 30 police had been posted outside the building after the Bharatiya Janata Yuva Morcha had announced a demonstration before Bidhan Bhavan on Saturday morning.

This was apparently part of a nationwide programme of protesting outside Congress headquarters to “condemn” Rahul Gandhi’s “lies and conspiracy” on the Rafale deal and demand an unconditional apology following what the BJP claims was a Supreme Court “clean chit”.

“But the police stood mute spectators most of the time —even when black ink was thrown at their uniforms. They threw black ink at me too,” Jabbar said.

“I’ve been here since 1996 (when Bidhan Bhavan was inaugurated) but never saw anything like this.”

State Congress chief Somen Mitra and Rajya Sabha member Pradip Bhattacharya, who arrived after the mob left around noon, were similarly incredulous.

“I’ve been in politics for over 50 years but never saw anything like this in Bengal,” Bhattacharya said. The Congress has lodged a police complaint.

Local shopkeepers and other eyewitnesses said the mob was mostly made up of men in their 20s and 30s, who wore saffron clothes and spoke Hindi.

“They tore down every banner, hoarding, flag and poster of the Congress they could find in the area. Some of them threw stones at the Bidhan Chandra Roy bust atop the boundary wall. The police did nothing,” a shopkeeper said.

Before leaving, the mob burnt an effigy of Rahul. By then they had defaced, stabbed with their flagpoles, or smeared with black ink every image they could find in the area of Rahul, Sonia Gandhi, Somen or the Congress’s leader in the Lok Sabha, Adhir Chowdhury.

“The chaos wasn’t pre-planned. Things got a little out of hand because of some overenthusiastic members,” a state BJP functionary said.

The Youth Congress organised a counter demonstration around 3pm, which it tried to take to the state BJP headquarters on Muralidhar Sen Lane in central Calcutta. But the police, who had already cordoned off the access points, were visibly active and arrested around 30 activists among the several hundred.

The protesters burnt an effigy of Prime Minister Narendra Modi and allegedly threw rotten eggs and black ink at the cops.

The two incidents threw traffic out of gear in and around the Moulali-Entally-Park Circus area in the morning and Central Avenue in the afternoon, for an hour each.

State BJP chief Dilip Ghosh said: “They (BJP youth) did nothing wrong by going there. But disrespecting anybody is never our intention.”