The UK “must be ready for Russian aggression for years to come”, the boss of MI5 warned as he laid bare the “very real threat” posed by hostile states.

Director general Ken McCallum said the UK is in a contest with “adversaries who have massive scale and are not squeamish about the tactics they deploy”, setting out in stark language the dangers from Russia, China and Iran.

In a speech from the security agency’s Thames House headquarters in London on Wednesday, Mr McCallum said there have been at least 10 potential plots this year by Iranian intelligence services to kidnap or kill British or “UK-based” people considered “enemies of the regime”.

Although he stressed Russian president Vladimir Putin is “not winning” the war in Ukraine, Mr McCallum said: “The serious point is that the UK must be ready for Russian aggression for years to come.

“Some of that will be covert aggression for MI5 to detect and tackle. But much of it … will be overt. Our national resilience, brought into sharp focus by Covid, is a vital asset in which we must invest.”

More than 600 Russian officials have been expelled from Europe since February, with more than 400 judged to be spies.

This “struck the most significant strategic blow against the Russian intelligence services in recent European history,” Mr McCallum said, though he added: “We shouldn’t be complacent.”

In the UK, 23 Russian spies posing as diplomats were removed and 100 more Russians were denied diplomatic visas on national security grounds.

Drawing on a football analogy to hammer home his concerns, Mr McCallum said Russia “thinks nothing of throwing an elbow in the face and routinely cheats to get its way”, adding: “They will keep attacking us.”

Meanwhile, Chinese authorities are “trying to rewrite the rulebook, to buy the league, to recruit our coaching staff to work for them”, while Iran “will only let people support one team and is prepared to use violence against those who don’t toe the line”.

“We’re alive to the risk of these teams loaning players to each other, amplifying their strengths”, he added as he highlighted Iran providing support to Russia by supplying drones “inflicting misery in Ukraine”.

Speaking in detail on the threat faced from Iran for the first time, he said the country is at times prepared to take “reckless action” and “projects threat to the UK directly through its aggressive intelligence services.

“At its sharpest, this includes ambitions to kidnap or even kill British or UK-based individuals perceived as enemies of the regime.

“We have seen at least 10 such potential threats since January alone. We work at pace with domestic and international partners to disrupt this completely unacceptable activity.”

Repeating warnings he made earlier this year, Mr McCallum said China is playing “the long game in cultivating contacts” to manipulate opinion in its favour.

“Since then, we’ve seen yet more concerning activity,” he added.

After mentioning the attack on a Hong Kong pro-democracy protester at the Chinese consulate in Manchester, he said: “We’re seeing further indications of that repression,” adding: “To intimidate and harass UK nationals or those who have made the UK their home cannot be tolerated.”

During the wide-ranging speech, Mr McCallum said while rising state threats are a “huge challenge”, getting ahead of terror plots is “still the first thing the British public expect of us”, as he said so-called lone wolf terrorists are “fiendishly hard to detect and disrupt”.

MI5 and the police have disrupted 37 late-stage terror attack plots since the start of 2017, an increase of eight since Mr McCallum gave his last update on threats last July.

Security services are seeing growing attempts by right-wing extremists to “acquire weapons”, particularly firearms, whether “illegally obtained, homemade or 3D-printed, “well in advance of any specific targeting intent developing”, Mr McCallum said.

There are also growing numbers of right-wing extremist “influencers” who “fuel grievances and amplify conspiracy theories” as part of what he called a “hateful soup” filled with Neo Nazism and white supremacy among other elements.

His comments come after last month’s firebombing of a migrant processing centre in Dover, Kent, was declared a terror attack once police found evidence the incident was motivated by an extreme right-wing ideology.

Asked why it took so long for police to conclude it was a terrorist incident, Mr McCallum – who called the attack “horrible” – said investigations are not always straightforward.

He said extreme right-wing terrorism is now a “diffuse online threat”, adding: “From the comfort of their bedrooms, individuals are easily able to access right-wing extremist spaces, network with each other and move towards a radical mindset.”

Terrorism inspired by Islamist ideology still accounts for about three-quarters of MI5’s terrorist caseload, Mr McCallum said.