Authorities in Tajikistan have detained nine people believed to have links to the Moscow concert hall shooting suspects, as well as terror group Islamic State Khorasan (IS-K), a security source has reportedly told the Reuters news agency.

All nine people were detained on Monday in the city of Vakhdat and have been brought to the capital, Dushanbe, the news agency reported, citing the unnamed source.

It comes after authorities in Moscow announced yesterday that the number of people killed in the 22 March attack on the Crocus City Hall had risen to 143. 

Four men, all identified as being citizens of Tajikistan, were arrested and charged with carrying out the attack.

A further eight people have been arrested on suspicion of aiding the attackers.

IS-K – a regional branch of the Islamic State terror group, which is active in south-central Asia – immediately claimed responsibility.

US intelligence also said it had information confirming the group was responsible.

Russian officials, however, have insisted that Ukraine and the West had a role – claims that Kyiv vehemently has denied.