The United States has designated the separatist group, the Baloch Liberation Army (BLA), as a foreign terrorist organisation, the US Department of State said on Monday.

The BLA, also known as the Majeed Brigade, is fighting for an independent Balochistan, which is a southwest province in Pakistan bordering Afghanistan.

In March, the BLA claimed responsibility for hijacking a Pakistani Jaffar Express train traveling from Quetta to Peshawar.

The incident saw the murder of 31 civilians and security personnel.

The BLA held over 300 passengers hostage, US Secretary of State Marco Rubio said in a statement.

Following the US' designation as a foreign terrorist organization, there will be restrictions on providing financial support to BLA and other aid to the group.