A Russian navy frigate and a nuclear-powered submarine churned into Havana harbour on Wednesday, a stopover the US and Cuba said posed no threat but was seen as a Russian show of force.

Cuba - a long-time ally of Russia - saluted the ships' arrival with cannon fire, while Russian diplomats waved Russian flags and took selfies as the vessels passed the harbour's historic fortresses.

The Admiral Gorshkov frigate, and later the nuclear-powered submarine Kazan, half submerged with its crew on deck, were accompanied by a tugboat and fuel ship that had arrived earlier in the morning.

The four Russian vessels sailed to Cuba after conducting "high-precision missile weapons" training in the Atlantic Ocean, according to Russia's defence ministry.

The submarine and frigate carry Zircon hypersonic missiles, Kalibr cruise missiles and Onyx anti-ship missiles, the ministry said.

Cuba said last week that the visit was standard practice by naval vessels from countries friendly to Havana.

The Cuban foreign ministry said the fleet carried no nuclear weapons, something echoed by US officials.

The US said it had been monitoring the Russian vessels as they skirted the nearby Florida coast, but said they posed no threat.

White House national security adviser Jake Sullivan told reporters on Wednesday such naval exercises were routine.

"We have seen this kind of thing before and we expect to see this kind of thing again, and I'm not going to read into it any particular motives," Sullivan said. (Reuters)