ST PETERSBURG, Russia (Reuters) -Overbearing in life but discreet in death, Russian mercenary chief Yevgeny Prigozhin was buried quietly in a leafy cemetery on the outskirts of St Petersburg on Tuesday, six days after he was killed in an unexplained plane crash.

The funeral took place away from the glare of the media and in stark contrast to the brazen, self-publicising style with which Prigozhin had fanned his reputation, in Russia and far beyond, for ruthlessness and ambition.

"The farewell to Yevgeny Viktorovich took place in a closed format. Those who wish to say goodbye may visit Porokhovskoye cemetery," his press service said in a short post on Telegram.

Prigozhin, two top lieutenants of his Wagner group and four bodyguards were among 10 people who died when his Embraer Legacy 600 private jet crashed north of Moscow on Aug. 23.

He died two months to the day after staging a brief mutiny against the defence establishment that posed the biggest challenge to President Vladimir Putin's rule since he rose to power in 1999.

Reuters photos and video late on Tuesday showed Prigozhin's grave strewn with flowers in the wooded cemetery, with a strong presence nearby of police officers and members of the Rosgvardiya national guard.

Independent news outlet Agentstvo quoted a cemetery employee as saying only 20 to 30 friends and family had attended the ceremony and that it lasted just 40 minutes.

The secrecy surrounding the event meant it could not be turned into a large-scale public show of support for Prigozhin, a brutal figure who was nevertheless admired by some in Russia for throwing his fighters into the fiercest battles of the war in Ukraine and speaking openly about the shortcomings of the Russian military and its leadership.

In recent days admirers had heaped flowers on makeshift shrines to Prigozhin in Moscow, St Petersburg and elsewhere.

The Kremlin has rejected as an "absolute lie" the suggestion that Putin ordered his death in revenge for the June mutiny. It said earlier on Tuesday that the president would not attend the funeral.

MUTINOUS MERCENARY

After months of insulting Putin's top brass with a variety of crude expletives and prison slang over their perceived failure to fight the Ukraine war properly, Prigozhin took control of the southern city of Rostov in late June.

His fighters shot down a number of Russian aircraft, killing their pilots, and advanced towards Moscow before turning back 200 km (125 miles) from the capital. Putin initially cast Prigozhin as a traitor whose mutiny could have tipped Russia into civil war, though he later did a deal with him to defuse the crisis.

The day after the crash, Putin sent his condolences to the families of those killed and said he had known Prigozhin for a very long time, since the chaotic years of the early 1990s.

"He was a man with a difficult fate, and he made serious mistakes in life," Putin said, while describing him as a talented businessman.

Before the mutiny, Prigozhin had quipped that his nickname should have been "Putin's butcher" rather than "Putin's chef" - a moniker acquired after his catering company won Kremlin contracts. He always professed loyalty to Putin, though he said his defence minister, Sergei Shoigu, was so incompetent he should executed for his treachery.

After Prigozhin's death, Putin ordered Wagner fighters to sign an oath of allegiance to the Russian state - a step that Prigozhin had opposed due to his anger at the defence ministry that he said risked losing the Ukraine war.

Investigators said on Sunday that genetic tests had confirmed the identities of all 10 people killed in the crash, who also included two pilots and a flight attendant.

Earlier on Tuesday, Valery Chekalov, the head of Wagner logistics, was buried at another St Petersburg cemetery. His family was joined by dozens of people, some of whom Reuters identified as Wagner mercenaries and employees from Prigozhin's business empire.

A Russian Orthodox priest said prayers and swung a censer before Chekalov's coffin, and mourners stepped forward to kiss it.

Prigozhin's right-hand man Dmitry Utkin, co-founder of Wagner and the group's top military commander, was also killed in the crash.

Uncertainty now surrounds the fate of Prigozhin's large business empire, including mercenary operations in several African countries where he struck big mining deals for gold and diamonds and was useful to the Kremlin in advancing Russian security interests in competition with rival powers such as France and the United States.

(Writing by Mark Trevelyan and Guy Faulconbridge; Editing by Jon Boyle and Alex Richardson)