BRUSSELS European Union foreign ministers on Monday said an aborted mutiny in Russia at the weekend showed Moscow's war in Ukraine was causing domestic instability and undermining its military power, but stressed their focus remained on supporting Kyiv.

Wagner mercenary forces under renegade leader Yevgeny Prigozhin seized control of military headquarters in southern Russia and began to move towards Moscow on Saturday before suddenly heading back to eastern Ukraine after a deal with the Kremlin.

"The political system is showing fragilities, and the military power is cracking," EU foreign policy chief Josep Borrell told reporters in Luxembourg as he arrived for a meeting with ministers from across the 27-member bloc.

"It's not a good thing to see that a nuclear power like Russia can go into a phase of political instability," Borrell said, adding this was the moment for the EU to continue supporting Ukraine more than ever.

Borrell said Russian President Vladimir Putin was paying the price for creating a "monster" with Prigozhin's Wagner mercenary group.

"The monster that Putin created with Wagner, the monster is biting him now, the monster is acting against his creator."

German Foreign Minister Annalena Baerbock said Putin was destroying his own country with his "brutal war of aggression" in Ukraine.

"We are seeing massive cracks in the Russian propaganda," she added.

Baerbock said the EU would focus on helping Ukraine in its fight to let its people live in peace and freedom.

The ministers stressed the mutiny was an internal Russian matter, with no outside involvement. But they also made clear it had implications far beyond Russia's borders.

"It would be absolutely dangerous for Europe if the biggest country of the world with the largest arsenal of nuclear weapons was to be shattered," Luxembourg's Foreign Minister Jean Asselborn said.

Austrian Foreign Minister Alexander Schallenberg said Putin should follow Prigozhin's example and "turn around".

Finnish Foreign Minister Elina Valtonen suggested the weekend's events showed Putin's hold on power was not as strong as it seemed.

"It is common for authoritarian states that everything seems to be very stable until one day, nothing is stable anymore. And I expect such a development for Russia as well," she told reporters.

(Reporting by Sabine Siebold, Bart Meijer and Andrew Gray; Editing by Conor Humphries)