Outspoken Russian hawk and firebrand Dmitri Medvedev has not stopped trolling Trump over the US nuclear submarine deployment, and the US President's annoyance over the issue continues to show.

The former Russian president and current Security Council Deputy Chairman has said in fresh remarks tinged with sarcasm that the situation brings to mind the saying about a black cat in a dark room.

"Donald Trump is once again talking about the submarines he moved ‘over to the coast of Russia," this time noting that they are 'totally' undetectable," he wrote on social media.

That's when he joked: "It's hard to find a black cat in a dark room, especially if there is no cat" - suggesting the notion that American nuclear subs are patrolling waters off Russia is a ruse.

This was an apparent response to Trump's words to a large gathering of US generals and admirals gathered from across the world at Quantico, wherein the US commander-in-chief boasted he had moved "a submarine or two" to the coast of Russia, before saying the word "nuclear" can never be said.

"I call it the N word. There are two N words, and you can't use either of them," he said. All of this hearkens back to the initial very public spat between Trump and Medvedev. To review of the early August exchange:

The day before, Trump had issued an ultimatum to Russia: If it does not agree to a ceasefire by next Friday, August 8, he will impose a package of economic sanctions.

The next day, Medvedev posted on social media, describing Trump’s threat as “a step towards war”. He wrote that Trump was “playing the ultimatum game with Russia”.

In a post on Truth Social, Trump responded: “Words are very important, and can often lead to unintended consequences, I hope this will not be one of those instances.”

Thankfully it has all so far been confined to social media barbs, and not any clear instance of either side's strategic forces being placed on emergency alert.

The US Navy's submarine fleet moves across the world mostly undetectable, and ideally at least - untraceable. But Medvedev is claiming Trump's boasts concerning a pair of nuclear submarines is empty and without evidence.

However, hopefully he doesn't provoke Trump too much at this ultra-sensitive moment of soaring tensions between Moscow and NATO. Of note is that Trump in his Tuesday speech at Quantico said that the US is about 20 years ahead of Russia in terms of nuclear technology and development.