USA: Pentagon officials urged the Russian military to focus its airstrikes in Syria on Islamic State (IS) fighters rather than opponents of Syrian President Bashar Assad.

Tensions between Washington and Moscow are escalating over Russian airstrikes that apparently are serving to strengthen Assad by targeting rebels rather than hitting IS fighters it promised to attack.

“What is important is Russia has to not be engaged in any activities against anybody but (the IS group),” US secretary of state John Kerry said.