Police on Saturday made the first arrest in connection with Thursday’s murders of three Trinamul leaders in Gopalpur area of Canning in South 24-Parganas.

Aftabuddin Sheikh, a Trinamul worker, was nabbed from Kultali during the early hours of Saturday, police said. Aftab was not named in the FIR but is believed to have been involved in the conspiracy. He was tasked with watching the movement of panchayat member Swapan Ghosh and inform assailants, police said.

Aftabuddin, the elder brother of Basir Seikh, named in the FIR, was arrested from a hideout in Kultali. A special investigating team formed by the superintendent of Baruipur police district spotted him late on Friday night by tracking his mobile phone location. He was caught in the small hours of Saturday and produced before a court in Canning that ordered him two weeks of police custody.

“Aftabuddin was involved in the conspiracy and present at the (murder) spot…. He is a big catch. His name surfaced during the course of investigation...We are optimistic that this arrest will give us a breakthrough to uncover the conspiracy behind the triple murders,” said a senior police officer of Baruipur police district.

On Thursday morning Trinamul's Gopalpur panchayat member Swapan Ghosh and close aides Bhutnath Pramanik and Jhantu Halder, both booth committee presidents, who were on a motorcycle, were stopped near Kochua Pear Park by half a dozen goons and shot at close range. Their throats were also slit. The trio were going to a nearby party office for a meeting in connection with the July 21 Martyrs’ Day rally in Calcutta.

The arrest of Aftabuddin, an active Trinamul worker in the area, has raised questions about the party leadership’s claim of the BJP’s involvement in the murders. On Saturday, Aftabuddin’s family claimed that a section of the party leadership had implicated him in the case.

However, a 13-member team of Trinamul leaders, including party MPs and MLAs, which visited Canning on Saturday, accused the BJP.

“The BJP has been trying to unleash terror across the state to increase its support base. The three murders in Canning are part of that desperate attempt. We came to meet the (bereaved) families on the directive of Mamata Banerjee and Abhishek Banerjee,” said MP Mala Roy.

However, local residents told the team that a section of party workers in the area had killed the three leaders.

The BJP state committee leader Sumit Das also said that the arrest of a Trinamul worker proved which party was behind the murders.

He said: “The arrest of a Trinamul worker proved well who were involved in the murder of the three Trinamul leaders. Let the police conduct an unbiased probe and see how big names of Trinamul surface.”

A local Trinamul worker said: “During the past eight months at least five leaders were killed and a few also had an attempt on their lives. But, every time a party worker is killed, police after initial alacrity turn inactive after nabbing some insignificant persons.… The masterminds remain elusive.”

The Trinamul team members handed each of the three families a cash compensation of Rs 4 lakh on behalf of the party.

Roy said: “We have told police to arrest the culprits at the earliest."