British Prime Minister David Cameron says Russia's continuing military intervention in Syria is making the situation worse.

He said Saturday that Russia's actions are supporting the "butcher" president of Syria, Bashar Assad.

Cameron said Russian President Vladimir Putin's military forces are not discriminating between Islamic State extremists inside Syria and more moderate opposition forces battling Assad.

Cameron called for a comprehensive plan to bring a political transition to Syria as the best way to end a lengthy civil war and bring peace to the region.

His comments echoed those made by President Barack Obama and other leaders in recent days.