The National Investigation Agency (NIA) has arrested a key accused in connection with its probe into the back-to-back violent attacks on the Indian high commission in London on March 19 and 22 last year, the federal agency said in a statement on Thursday.

This is the first arrest in the case, the agency said.

Inderpal Singh Gaba, a resident of Hounslow, UK, has been arrested in Delhi by the agency for his alleged role, particularly the March 22 attack, in which over 2,000 pro-Khalistan supporters vandalised the high commission building and threw articles including ink to deface it, NIA said.

On March 19, a smaller group pulled down the Indian flag in an attack that also led to injuries to some embassy staff.

The protestors were organised by UK-based Sikh radical and Khalistan Liberation Force (KLF) leader Avtar Singh Khanda, who later died in a UK hospital in June 2023. Khanda was a close associate of Khalistani terrorist Jagtar Singh Tara, and allegedly acted in retaliation to the action taken by Punjab police against Waris Punjab De chief Amritpal Singh on March 18. Singh is currently lodged in a high-security prison in Assam.

“In a major breakthrough, the NIA on Thursday arrested one accused in the 2023 case relating to the violent attack on the High Commission of India, London, and unlawful actions during the subsequent protests,” an NIA spokesperson said in a statement on Thursday.

The spokesperson said Gaba was arrested for carrying out unlawful activities during the March 22, 2023 protests. The agency, however, didn’t reveal if Gaba was arrested at the airport or the purpose of his visit here. The agency also didn’t disclose his exact role in the attack or his association with pro-Khalistani leaders.

NIA said the incidents in London on March 19 and 22 last year were parts of a larger conspiracy to unleash vicious attacks on the Indian missions and its officials. “The attacks in London were found to be in retaliation to the action taken by Punjab police against pro-Khalistani separatist Amritpal Singh on March 18, 2023”.

A NIA team travelled to London in May 2023 to gather evidence with the help of the Metropolitan police. After the visit, the agency released CCTV footage of the attack and the suspects, identifying at least 45 suspects from the mob that carried out the March 19 attack.

Look-out circulars (LOCs) have also been issued against about a dozen suspects involved in the attacks and officials, who didn’t want to be named, said other accused persons will also be identified soon through questioning of Gaba.

In August last year, the agency raided 31 locations across Punjab and Haryana in connection with the probe into the case.

NIA is investigating a larger conspiracy by Pakistan-backed pro-Khalistan leaders in the UK behind the incident. It took over the probe from the Delhi Police in both attacks after the ministry of home affairs (MHA) official met with their counterparts from the UK home office in April and flagged the high commission’s security and the challenges due to radicalisation of Sikh youth in the UK.

According to officials, the attack was allegedly organised by Gurcharan Singh of Dal Khalsa, UK; Avtar Singh Khanda of KLF, and many of their associates, both Indian and foreign nationals, who have been identified during the ongoing NIA investigations.

Avtar Singh Khanda was the main planner of the attacks and also played a key role in the rise of Amritpal Singh.

Khanda was a close aide of Paramjit Singh Pamma, who is associated with Babbar Khalsa international (BKI) and is known for holding theoretical radical training classes for the Sikh youth to mislead them.

A senior official in a central intelligence agency, who didn’t want to be named, said “Khanda propped up Amritpal Singh in association with the Pakistani spy agency ISI, and also worked as an ideologue for Sikh youngsters and brainwashed them against the Indian government”.

Agencies also believe that Khanda, along with Pamma, and other Khalistanis such as Sikhs for Justice (SFJ) leader Gurpatwant Singh Pannun, Gursharan Singh, and Jasvir Singh were “working on a deadly plan to destabilising Punjab”.

Pannun, based in the US, is a key person behind organising demonstrations and on-ground campaigns outside Indian high commissions in the UK, the US, Canada, Germany and other countries, according to this intelligence officer. SFJ was banned on July 10, 2019, for its anti-India activities while Pannun was declared a terrorist on July 1, 2020.