Yevgeny Prigozhin, a former Putin ally and founder of the Wagner army, said his men reached within 200 km of the capital on Saturday.
Earlier, Moscow deployed soldiers in preparation for their arrival and told residents to avoid going out.
The Wagner fighters captured the city of Rostov hundreds of kilometres to the south before racing in convoy through the country, transporting tanks and armoured trucks and smashing through barricades set up to stop them, video showed.
On Saturday night, Wagner fighters loaded tanks on trailers and began withdrawing from the Rostov military headquarters they had seized.
"In 24 hours we got to within 200 km of Moscow. In this time we did not spill a single drop of our fighters' blood," Prigozhin, dressed in full combat uniform at an undisclosed location, said in a video.
"Understanding ... that Russian blood will be spilled on one side, we are turning our columns around and going back to field camps as planned."
Reuters could not independently verify how far Prigozhin's mercenaries had reached.
The office of Alexander Lukashenko said the decision to halt further movement of Wagner fighters was brokered by the Belarusian president, with Putin's approval, in return for guarantees for their safety.
Kremlin spokesman Dmitry Peskov said Prigozhin would move to Belarus under the deal.
Peskov said Lukashenko had offered to mediate because he had known the mercenary leader personally for about 20 years.
Wagner's lightning insurrection appeared to develop with little pushback from Russia's regular armed forces, raising questions about Putin's hold on power in the nuclear-armed nation even after the abrupt halt to Wagner's advance.
Earlier, Prigozhin said what he called a "march for justice" was intended to remove corrupt and incompetent Russian commanders he blames for botching the war in Ukraine.
In a televised address from the Kremlin, Putin earlier said the Wagner rebellion put Russia's very existence under threat.
"We are fighting for the lives and security of our people, for our sovereignty and independence, for the right to remain Russia, a state with a thousand-year history," Putin said, vowing punishment for those who "prepared an armed insurrection".
Ukrainian President Volodymyr Zelenskiy said the Wagner revolt, which sparked a flurry of high-level calls between Western leaders, exposed turmoil in Russia.
"Today the world can see that the masters of Russia control nothing. And that means nothing. Simply complete chaos. An absence of any predictability," Zelenskiy said in his nightly video address.
Video obtained by Reuters showed troop carriers and two flatbed trucks each carrying a tank driving 50 km beyond the town of Voronezh, more than halfway to Moscow.
A helicopter fired on them near Voronezh, where a fuel depot exploded in a fireball shortly after a helicopter flew by, video obtained by Reuters showed.
The fighters led by Prigozhin, a former convict, include thousands of ex-prisoners recruited from Russian jails.
His men fought the bloodiest battles of the 16-month Ukraine war, including for the eastern city of Bakhmut.
He railed for months against the military's top brass, especially Defence Minister Sergei Shoigu and the chief of the general staff, Valery Gerasimov, accusing them of incompetence and of withholding ammunition from his fighters.
This month, he defied orders to sign a contract placing his troops under Defence Ministry command.
He launched the apparent mutiny on Friday after alleging that the military had killed many of his fighters in an air strike. The Defence Ministry denied this.
He said he had captured the headquarters of Russia's Southern Military District without firing a shot in Rostov, which serves as the main rear logistical hub for Russia's entire invasion force in Ukraine.
The surrounding area is also an important oil, gas and grains region.
Residents of the city had milled about calmly, filming on mobile phones as Wagner fighters in armoured vehicles and battle tanks took up positions.
One tank was wedged between stucco buildings with posters advertising a circus. Another had "Siberia" daubed in red paint across the front, an apparent statement of intent to sweep across the breadth of Russia.
Western capitals said they were closely following the situation. US President Joe Biden spoke with the leaders of France, Germany and Britain, while Secretary of State Antony Blinken spoke to G7 counterparts.
The insurrection risked leaving Russia's invasion force in Ukraine in disarray, just as Kyiv is launching its strongest counteroffensive since the war began in February last year.
Ukraine's military said on Saturday its forces made advances near Bakhmut, on the eastern front, and further south.
