Earlier on Wednesday, Russia's upper house of parliament unanimously approved the use of Russian armed forces in Syria after receiving a request for assistance from Damascus. According to the Kremlin, this decision only covers the use of the country's air force.
"Russia now joins all the [other] countries who think that by bombing Syria and Iraq you might promote peace. My idea is that… there has been no proof that this is going to function," Kox said on the sidelines of a PACE session.
Syria has been in a state of civil war since March 2011. Government forces have been fighting both "moderate" opposition factions and extremist groups.
A US-led international coalition has been conducting airstrikes against IS positions in Iraq since August 2014, later expanding their attacks to include IS targets in Syria, without the approval of Damascus or the UN Security Council.