(This March 31 story was refiled to remove picture)
LONDON (Reuters) - Russia accused Ukraine on Thursday of laying hundreds of mines near its coast and said some were drifting into open waters of the Black Sea and creating dangers for merchant shipping, a day after Kyiv said Moscow was responsible for planting mines.
The Black Sea is a major shipping route for grain, oil and oil products. Its waters are shared by Bulgaria, Romania, Georgia and Turkey as well as Ukraine and Russia, which have been at war since President Vladimir Putin invaded his southern neighbour on Feb. 24.
Ukraine's foreign ministry said on Wednesday that Russia was planting naval mines in the Black Sea as "uncontrolled drifting ammunition", turning them "into a de facto weapon of indiscriminate action".
Russia's defence ministry said on Thursday that from Feb. 24 to March 4, the remnants of the Ukrainian navy's mine-sweeping forces had placed about 420 sea anchor mines - 370 in the Black Sea and 50 in the Sea of Azov.
"As a result of storms in the Black Sea and due to unsatisfactory technical condition, cables with bottom anchors broke on about 10 Ukrainian mines," the defence ministry said.
"Since then, under the influence of wind and surface currents, Ukrainian mines have drifted freely in the western part of the Black Sea in a southerly direction ... No one can know where the remaining Ukrainian mines are drifting today."
Russia said Ukraine had "created a direct mine threat to transport and cargo ships of all Black Sea countries". Ukrainian officials did not immediately respond to a request for comment.
Earlier this month Russia's main intelligence agency accused Ukraine of laying mines to protect ports and said several hundred of the explosives had broken from cables and drifted away. Kyiv dismissed that account as disinformation.
In recent days Turkish and Romanian military diving teams have been involved in defusing stray mines around their waters.
Turkey's defence ministry said it had not yet identified the source and number of drifting mines and had been in contact with Ukrainian and Russian counterparts over the issue.
Tayfun Ozberk, a former senior officer with Turkey's navy, told Reuters it was difficult to determine reliable information on the mines which were being used by both Russia and Ukraine.
"Considering that it has been under a blockade for about two months, it seems very unlikely that Ukraine has recently laid mines," Ozberk said.
"In order for there to be 420 free floating mines, Ukraine must have laid 2,000-2,500 mines here. Because every mine you lay does not break, either. Therefore, the possibility that Ukraine may have just mined this area does not make much sense to me."
Ozberk said it was unlikely for even old mines to break away from their thick chains in large numbers.
Yoruk Isik, Istanbul-based geopolitical analyst and head of the Bosphorus Observer consultancy, said if the mines threat got bigger it could require an international response including help from Spanish, Italian, French and Greek vessels.
London's marine insurance market has widened the area of waters it considers high risk in the region and insurance costs have soared.
Five merchant vessels have been hit by projectiles - with one of them sunk - off Ukraine's coast, with two seafarers killed, shipping officials say.