LONDON, July 17 (Reuters) - Insurers are reviewing whether to freeze cover for any ships willing to sail to Ukraine after Russia said on Monday it will suspend participation in a UN-backed deal that allows the export of grain through a Black Sea safe corridor, sources said. "Due to the collapse of the Black Sea corridor deal, most shipowners will now refrain from calling Ukrainian ports," Christian Vinther Christensen, chief operating officer with Danish shipping group NORDEN told Reuters. The (key) question is whether Russia mines the area which would effectively cease any form of cover being offered," one insurance industry source said. The Lloyd's of London insurance market has already placed the Black Sea region on its high-risk list. Additional war risk insurance premiums, which are charged when entering the Black Sea area, need to be renewed every seven days.

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Persons: Christian Vinther Christensen, Neil Roberts, shipowners, Jonathan Saul, Sharon Singleton Organizations: NORDEN, Reuters, . Insurance, Lloyd's Market Association, Thomson Locations: Ukraine, Russia, UN, Turkey, London, Lloyd's