According to the prime minister, the world can not afford another Iraq or Afghanistan, adding that modern democracy is not realized in these countries. The region, instead, has seen wars and terrorism, which forced people to leave their homeland.

French Prime Minister Manuel Valls, in a head-to-head debate with Medvedev, pressed Russia to stop bombing civilians in Syria while commenting on Russian actions in the war-torn Middle East country which is also facing terrorist insurgency.

"France respects Russia and its interests... But we know that to find the path to peace again, the Russian bombing of civilians has to stop," Valls told the conference.

Russia has been accused of causing civilian casualties since it started air strikes targeting the Islamic State (IS) four months ago.

Medvedev rejected on Saturday the accusations as "just not true."

"There is no evidence of our bombing civilians, even though everyone is accusing us of this," he told the security conference.

"Russia is not trying to achieve some secret goals in Syria. We are simply trying to protect our national interests," Medvedev said, adding that Moscow wanted to prevent militant extremists getting to Russia.

He stressed that the West and Russia had common enemies in Syria, namely terrorists, and the two sides should strengthen their cooperation in the fight against terrorism.

As for Ukraine, Kerry urged Russia to fully implement the Ukraine peace agreement reached in Belarus' capital Minsk last year. Otherwise, he said, Russia would continue to face damaging economic sanctions, although "sanctions are not an end in themselves."

Poroshenko, who made very emotional remarks on the Ukraine conflict in a panel discussion, accused Russian troops of having "occupied" his country.

Medvedev, in his earlier statement, stressed that the Minsk agreements "are the best way to solve the crisis in Ukraine" and "should be followed by all sides."