The Russian paramilitary group Wagner made headlines overnight and into Saturday after the group's owner and leader, Yevgeny Prigozhin, vowed to strike back against the Russian military over allegations that government troops had killed a significant number of his private mercenaries.

In a nutshell, Prigozhin claims that Russian troops fired on and killed his own men as the latter fought in eastern Ukraine. The private group and the Russian military have been butting heads recently over the direction of the Ukrainian war and the credit due to the private group over its conduct in it. Prigozhin has also publicly criticized the Kremlin for not sending them enough ammunition and supplies, leading to deaths of his fighters.

In a proactive display of retaliation, Wagner troops have marched on and seized the key southern Russian city of Rostov-on-Don. Putin, meanwhile, has indicated that there will be a swift and severe retaliation for the military action:

"Those who carry deliberately on a path of treason, preparing an armed rebellion when you were preparing terrorist attacks, will be punished."

Prigozhin has vowed to continue to Moscow and appears to be on his way already. Security has been greatly heightened at the capital city and important military sites near it. Russia's Federal Security Service — the successor to the Soviet KGB — has reportedly opened a criminal case against the paramilitary leader.

And Putin has ordered his military to crush the Wagner coup.

In the recent past, Prigozhin has been a sharp critic of Russia's elite class for what he said has been wasteful and profligate conduct during the Ukrainian war. He has even criticized Vladimir Putin, which is a big no-no in Russia.

Here is Putin's address to Russia about the uprising:

UPDATE: Aaaand it's over.

The greatest challenge to Russian President Vladimir Putin in his more than two decades in power fizzled out after the rebellious mercenary commander who ordered his troops to march on Moscow abruptly reached a deal with the Kremlin to go into exile and sounded the retreat.

The brief revolt, though, exposed vulnerabilities among Russian government forces, with Wagner Group soldiers under the command of Yevgeny Prigozhin able to move unimpeded into the Russian city of Rostov-on-Don and advance hundreds of kilometers (miles) toward Moscow. The Russian military scrambled to defend Russia's capital.

Under the deal announced Saturday by Kremlin spokesman Dmitry Peskov, Prigozhin will go to neighboring Belarus, which has supported Russia's invasion of Ukraine. Charges against him of mounting an armed rebellion will be dropped.

The government also said it would not prosecute Wagner fighters who took part, while those who did not join in were to be offered contracts by the Defense Ministry. Prigozhin ordered his troops, many of whom had been fighting alongside Russian regular soldiers in Ukraine, back to their field camps.