Russia has detained an Uzbek citizen who investigators believe placed the bomb that killed Lt Gen Igor Kirillov on the instructions of Ukraine’s security service, the country’s investigative committee has said.

The 29-year-old had allegedly been recruited by Ukrainian special services and promised $100,000 and travel to the European Union, the news agency Tass reported, citing the country’s domestic spy agency, the FSB.

The man was arrested in the village of Chernoye in the Balashikha district of Moscow, the news agency Ria reported, citing interior ministry spokesperson Irina Volk.

Kirillov, the head of the military’s chemical, biological and radiological weapons unit, was killed along with his assistant when a bomb hidden in an electric scooter went off as the two men left a building in a residential area in south-east Moscow on Tuesday.

Kirillov was the most senior Russian military officer to be assassinated inside Russia. Ukraine’s SBU intelligence service, which accused him of being responsible for the use of chemical weapons against Ukrainian troops, something Moscow denies, took responsibility for the killing.

Russia’s investigative committee, which investigates serious crimes, said in a statement on Wednesday that the unnamed suspect had told them he had come to Moscow to carry out an assignment for Ukraine’s intelligence services.

In a video of the confession published by the Baza news outlet, which is known to have sources in Russian law enforcement circles, the suspect is seen sitting in a van describing his actions. It was not clear under what conditions he was speaking and Reuters could not immediately verify the video’s authenticity.

Dressed in a winter coat, the suspect is shown saying he had come to Moscow at the orders of Ukraine’s intelligence services, bought an electric scooter, and then received an improvised explosive device to carry out the attack months later.

He describes how he had placed the device on the electric scooter, which he had parked outside the entrance of the apartment block where Kirillov lived. Investigators cited him as saying that he had set up a surveillance camera in a hire car nearby and that the organisers of the assassination, who he was cited as saying had been based in the Ukrainian city of Dnipro, had used the camera to watch what was going on.

The suspect, who was born in 1995, is shown saying that he had remotely detonated the device once Kirillov had left the building.

He says Ukraine had offered him $100,000 for his role in the murder and residency in a European country.

Investigators said they were identifying other people involved in the killing and the daily Kommersant newspaper reported that one other suspect had been detained.

Reuters contributed to this report