The west is failing to get to grips with Russian hacking and fake news, the Latvian foreign minister, Edgars Rinkēvičs, has said.

Speaking on a visit to London, Rinkēvičs said there was increasing evidence that Russia was automating disinformation on social media. Pointing to new Nato-sponsored research showing more than five times the number of Russian language tweets sent in Latvia concerning Nato came from bots, instead of from individuals. The figure in Estonia was nine times as many. He described the tactic as ”very systematic and a new way to spread propaganda amongst young people”.

He urged US Congress to press ahead with its inquiry into Russian interference in the 2016 US election, saying “it is essential for all US allies to understand the mechanics of how you combine cyber attack and then use it as [an] information weapon to influence people’s opinions”.

Rinkēvičs said: “If you have hacking, fake news with a purpose, it is very difficult to react. We can find out what happened, but it is very difficult to prove. The whole law in this area needs addressing.”

Rinkēvičs was attending a new joint Nordic-Baltic-UK forum of eight foreign ministers in London that was convened by the UK foreign secretary, Boris Johnson, the first such meeting to be held at foreign ministers level.

He denied the meeting was designed to coordinate Brexit strategy among nations historically sympathetic to Britain, saying the EU negotiating position remained united. He said he would like to see the UK remain involved in EU foreign and defence policy after Brexit, but said the precise mechanism remained to be discussed.

Johnson stressed Britain’s continuing role in Nato, as well as its leading military role sending 800 troops to lead a battlegroup in Estonia designed to deter Russian aggression in the region.

The London meeting comes as a large Russian military exercise on Europe’s eastern flank is about to take place.

Russia claims the Zapad 17 exercise will include just over 10,000 troops, with only 3,000 of those entering Belarus to help the Belarus army “quell” an imaginary separatist uprising supported by Nato member countries. Critics claim the exercise is in fact intended to simulate an attempted joint invasion of Poland and Lithuania with the aim of cutting the supply of Nato reinforcements.

However, Rinkēvičs claimed the number of Russian troops involved would be closer to 100,000 once all the exercises under way were counted, and said it was likely to feature a “nuclear element”.

“We have sufficient reason to believe this exercise will have a nuclear element. Later in September we will see what form, but last time it took the form of a preventative strike,” he said.

Part of the preparation involves airlifting missiles to the tactical short range Iskander ballistic missile units.