Russia's request to allow its ships to stop on Spanish territory "are under review" while Spain weighs input from its allies and Russian authorities, a foreign ministry spokesman told daily newspaper El Pais late Tuesday.
Spain's foreign ministry did not immediately respond to requests for information on Wednesday.
The spokesman's statement appears to confirm reports that part of a Russian flotilla -- led by the aircraft carrier Admiral Kuznetsov -- was expected to take on fuel and supplies at the port of Ceuta, a Spanish territory on the north coast of Africa.
Russia announced earlier this month that the Admiral Kuznetsov, part of its Northern Fleet, would be sent to the eastern Mediterranean to boost its naval forces in the area.
Russia has been staging a bombing campaign in Syria for the past year in support of President Bashar al-Assad and has deployed a naval contingent to back up its operation.
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NATO Secretary-General Jens Stoltenberg expressed concern Tuesday that the flotilla could take part in Syria air strikes.
"It is up to each country to decide if these ships can refuel in different ports en route to the eastern Mediterranean," he said.
"I think all NATO members are aware that this group could be used to carry out air attacks on Aleppo and Syria," he added.
Britain was more direct.
"Her Majesty's government has previously expressed concerns to the Spanish government about its hospitality to the Russian navy when we have concerns about Russia's military activity," a British government spokesman said.
"Access to Spanish ports is a matter for the Spanish authorities," he added.
Spain, a NATO member, regularly allows Russian war ships to stop in Ceuta.