A Russian ship carrying helicopters and missiles for Syria was stopped off Scotland after its insurance was canceled at the request of London, the insurer said.

The Russian cargo ship MV Alaed -- believed to be carrying Mi25 helicopters and munitions -- was temporarily stopped near the Hebrides archipelago off Scotland's west coast after it evaded authorities near the Dutch coast, security sources told the British newspaper The Daily Telegraph.

"We were made aware of the allegations that the Alaed was carrying munitions destined for Syria," the British marine insurer Standard Club said in a statement. "We have already informed the ship owner that their insurance cover ceased automatically in view of the nature of the voyage."

British security officials said they told Standard Club that providing insurance to the shipment was likely to be a breach of European Union sanctions against the Syrian regime.

They said they were continuing to monitor the ship, which has been the subject of a fierce war of words between Washington and Moscow after U.S. Secretary of State Hillary Clinton last week alleged it was adding to the arsenal of weaponry available for Syria President Bashar Assad to use against rebellious Syrian towns.

"We have various ways of keeping track of this ship and that is what we are doing," a source told the Telegraph.

Large Mi-25 helicopter gunships and attack helicopters, first used by the Soviet air force in 1972, were sometimes called "flying tanks" by Soviet pilots, but are more commonly nicknamed "Crocodiles" due to the helicopter's camouflage scheme and "Glass" because of the flat glass plates that surround the cockpit.

The MV Alaed allegedly picked up the helicopters from the Russian port of Kaliningrad, bordering NATO and EU members Poland and Lithuania on the Baltic Sea.

U.S. President Barack Obama and Russian President Vladimir Putin Monday called for an end to the bloodshed in Syria and expressed support for a political transition in the strife-ridden country.

"We are united in the belief that the Syrian people should have the opportunity to independently and democratically choose their own future," Obama and Putin said in a joint statement released after a two-hour meeting on the sidelines of the Group of 20 Summit in Los Cabos, Mexico.