Belarusian citizens fighting in Ukraine's east on either side of the conflict will be jailed.
Belarusian KGB chief Valery Vakulchyk told journalists in Minsk on October 2 that any Belarusians found to have fought in Ukraine will be defined as "mercenaries," which are banned under Belarusian law.
People in Belarus found have acted as a mercenary can be sentenced to up to seven years in jail.
Media reports in Belarus said in August that some individuals have been recruiting people in Belarus to fight for pro-Russian separatist forces in Ukraine's eastern regions of Donetsk and Luhansk.
There were also reports of Belarusian volunteers fighting for Ukraine against the separatists.
Ukrainian armed forces have been fighting against pro-Russian separatists in the country's east for six months.