(Adds background on Russian battle group)

BRUSSELS, Oct 25 (Reuters) - A Russian naval battle group heading for Syria could be used to target civilians in the besieged city of Aleppo NATO Secretary-General Jens Stoltenberg warned on Tuesday, calling on Moscow to implement a lasting ceasefire.

"The battle group may be used to increase Russia's ability to take part in combat operations over Syria and to conduct even more air strikes against Aleppo," Stoltenberg said.

"The concern is that the carrier group can be used as a platform for increased air strikes against civilians in Aleppo," he told a news conference.

The battle group, which passed through the English Channel on Friday, is made up of Russia's only aircraft carrier Admiral Kuznetsov, as well as a nuclear battle cruiser, anti-submarine warships and support vessels, likely escorted by submarines, NATO officials said.

The naval deployment, a rare sight since the end of the Soviet Union, is carrying fighter bombers and helicopters and is expected to join around 10 other Russian vessels already off the Syrian coast, diplomats said.

(Reporting by Robin Emmott; editing by Philip Blenkinsop) ((philip.blenkinsop@thomsonreuters.com; +32 2 287 6838; Reuters Messaging: philip.blenkinsop.thomsonreuters.com@reuters.net))