Austria has declared four Russian diplomats persona non grata.

The diplomats were already known to Austrian authorities and had been under the scrutiny of intelligence services for some time, according to vedomosti.ru.

Three of the diplomats worked at the Russian Embassy in Vienna. The fourth was stationed at the Vienna office of the Organization for Security and Co-operation in Europe (OSCE).

The diplomat based at the OSCE office was a member of the Russian delegation dealing with military security and arms control issues.