* UK told Moscow defence shipments must stop
* Syria receiving military hardware in ships
LONDON/MOSCOW June 19 (Reuters) - A cargo ship now moving off the north-west coast of Scotland is believed to be carrying Russian weaponry to Syria, according to an insurer which says it has withdrawn coverage for the vessel.
Britain said it was aware of a consignment of refurbished Russian-made attack helicopters heading for Syria, but did not say if it was referring to the same vessel.
Russia has faced increasing Western criticism over arms supplies to Syria, where the United Nations says government forces have killed more than 10,000 people in a crackdown. Last month, the U.S. described the delivery of heavy Russian weapons in a shipment as "reprehensible".
Ship tracking data showed on Tuesday that the Curacao-flagged cargo ship Alaed set off from the Russian port of Baltiisk in the province of Kaliningrad on June 11.
London-headquartered ship insurer Standard Club said it had been contacted about the vessel it had been covering, but did not say by whom.
"We were made aware of the allegations that the Alaed was carrying munitions destined for Syria and have already informed the ship owner that their insurance cover ceased automatically in view of the nature of the voyage," the insurer said.
Moscow-based Russian ship management and operator group Femco, operating the Alaed, offered no comment when contacted several times by Reuters about the ship and its cargo. But it said it would post comment on its website later in the day with "true information".
Insurers would be obliged to withdraw coverage for any shipments violating European Union sanctions, including an arms embargo on Syria. Without insurance, the vessel could be forced either to dock at a port, drop its run to Syria or find a provider outside the European Union.
The Alaed was last seen off the coast of Scotland and declared as heading for the Russian port of Vladivostok where it was due to arrive on July 24, tracking data showed on Tuesday.
A British Foreign Office spokeswoman said London was aware of "a ship carrying a consignment of refurbished Russian-made attack helicopters heading to Syria", but did not say whether she was referring to the Alaed.
"We are working closely with international partners to ensure that we are doing all we can to stop the Syrian regime's ability to slaughter civilians being reinforced through assistance from other countries."
A Moscow-based defence analyst said the Alaed was carrying helicopters that were bought by Syria during the Soviet era and had been sent back to Russia for repair in the Baltic Sea exclave of Kaliningrad.
"I am sure based on open source material that the ship is carrying 12-15 helicopters that were repaired in Kaliningrad and are on their way to Syria," said Ruslan Aliyev, who works at defence think tank CAST, referring to an order of M-25 helicopters.
"They were old helicopters bought by (Assad's late father and predecessor) Hafez al-Assad, I believe at the end of the 1980s."
U.S. Secretary of State Hillary Clinton said on June 12 that the United States was "concerned about the latest information we have that there are attack helicopters on the way from Russia to Syria." She said such a sale "will escalate the conflict quite dramatically."
The accusation angered Moscow, which says it is fulfilling existing contracts for air defence systems, for use against external attacks, and not delivering offensive weapons. Under pressure over continuing arms trade with Syria, President Vladimir Putin said earlier this month that the weapons its sends could not be used in civil conflicts.
The Russian Foreign Ministry said last week that Russia had sent no new helicopters to Syria but had repaired helicopters delivered to its government "many years ago". It gave no specifics about when any helicopters were repaired or sent back to Syria.
SHIPMENT HALT URGED
A source close to Russia's arms exporting monopoly Rosoboronexport said last week that Clinton may have been referring to helicopters that were sent to Russia in 2009 for repairs and may have been on the way back to Syria.
The source said at least nine Mi-25 helicopters were sent to Kaliningrad to be repaired by Oboronservis, owned by the Defence Ministry.
A spokesman for insurer Standard Club said the company informed about termination of cover was Femco.
A rights group reported that the Professor Katsman ship had docked at the Syrian port of Tartous last month with a cache of heavy weapons for Assad. (Additional reporting by Mohammed Abbas in London)