The suspects are said to have sent packages containing homemade explosive devices to other European countries via courier services, the Lithuania-based prosecutor said in a statement.

The 15 people are accused of terrorism offences after fires broke out last year in Germany, Poland and the UK.

The Metafrax Chemicals plant in Gubakha, Perm Krai, is subject to international sanctions by the U.K. and Ukraine.

NATO will launch a new deterrence initiative called "Eastern Sentry" in response to Russia's drone attack on Poland, the military alliance's secretary general Mark Rutte announced on Sept. 12.