Nearly 500,000 Russian soldiers have been killed since Moscow launched its full-scale invasion of Ukraine in 2022, according to Britain's top intelligence agency.

The figures were revealed by Anne Keast-Butler, director of the British Government Communications Headquarters (GCHQ), in her speech after taking office.

Both Kyiv and Moscow regularly publish estimates of the opposing side's casualties, but have been reluctant to detail their own.

However, in February, President Volodymyr Zelensky claimed that Ukraine had lost 55,000 soldiers since 2022.

The BBC Russian service has been counting Russian casualties in the war, together with the independent media Mediazona and a group of volunteers since February 2022.

A list is maintained of identified individuals whose deaths we have been able to confirm through official reports, newspapers, social media, and memorials and graves.

So far, the BBC has been able to confirm the names of 223,539 soldiers and officers who died while fighting on the Russian side in Ukraine.

The actual number of victims is believed to be much higher, and military experts we consulted estimate that our analysis of cemeteries, memorials and obituaries could represent between 45% and 65% of the total.

Accusations against Russia

Speaking from Bletchley Park, the military facility where German codes were broken during World War II, Keast-Butler singled out Russia for “attacking critical infrastructure, democratic processes, supply chains and the public trust.”

The Kremlin denies the accusations.

Keast-Butler also warned that Russia and China make large investments in space, both for peaceful and military purposes.

She said GCHQ is focused on repelling cyberattacks and countering what she called “reckless sabotage and assassination attempts.”

“In the face of such aggression and chaos, GCHQ is working tirelessly with intelligence and defense partners to weaken and reduce the Russian threat,” he said.

The Kremlin, which denies these accusations, has been held responsible for the murder of former KGB officer Alexander Litvinenko, after he was poisoned with radioactive polonium in his tea in a London hotel in 2006.

Russian authorities were also blamed for the attempted murder of a former Russian military intelligence officer, Sergei Skripal, in Salisbury in 2018, after he smeared the deadly nerve agent Novichok on the doorknob of his home.

More recently, since Russia's large-scale invasion of Ukraine and the UK's continued support for Ukraine, Moscow has been accused of waging a "hybrid war" against Western countries.

In her speech, the head of GCHQ added: “While we remain steadfast in our support for Ukraine, Putin is retreating on the battlefield.”

Hundreds of ships from Russia's so-called "ghost fleet" have entered British waters since the Prime Minister threatened to intercept them earlier this year, BBC Verify analysis suggests.

China's capacity

China is now a scientific and technological superpower, Keast-Butler said, with sophisticated capabilities “in its intelligence, cyber and military agencies.”

Regarding the advancement of artificial intelligence technology around the world, he warned that the room for maneuver for the United Kingdom and its allies to stay ahead of their rivals is shrinking.

“The ground beneath our feet is changing and changing rapidly,” he said.

"Cybersecurity is a critical priority for all businesses. Our experts are providing unprecedented levels of advice and guidance, but we need businesses to take immediate action," he said.

“Not only to protect livelihoods and customers, but for the frontline defense of our nation and our economy.”

Keast-Butler sees collaboration with the tech industry, academia, and even the public as key to staying up to date on advances in cybersecurity.

GCHQ tasks

GCHQ spends much of its time combating organized criminal networks bent on targeting vulnerable British businesses with phishing and ransomware attacks.

Keast-Butler urged everyone to ensure their own cybersecurity “from the boardroom to the living room.”

“At home, that means taking important steps right now to change passwords to access keys, and for society at large, it means integrating security into new technologies, protecting supply chains and making cybersecurity ten times more urgent,” he added.

GCHQ is the largest of the UK's three spy agencies, along with the Security Service (MI5) and the Secret Intelligence Service (MI6).

Headquartered in Cheltenham and housed in a huge circular building known as “the Donut”, GCHQ focuses on cybersecurity and signals intelligence.

Given its focus on cutting-edge technology, it consumes the majority of the national intelligence budget.

Additional reporting by Olga Ivshina of the BBC Russian service.