WATCH: Pentagon holds briefing as Russia drops charges against mercenary leader Prigozhin

The Pentagon held a news briefing Tuesday as Russia dropped its charges against mercenary chief Yevgeny Prigozhin.

Watch the briefing in the player above.

Russian authorities said Tuesday they have closed a criminal investigation into the aborted armed rebellion led by mercenary chief Yevgeny Prigozhin and are pressing no charges against him or his troops.

READ MORE: Russia drops charges against Prigozhin and others who took part in aborted armed rebellion

The Federal Security Service, or FSB, said its investigation found that those involved in the mutiny, which lasted less than 24 hours after Prigozhin declared it Friday, “ceased activities directed at committing the crime,” so the case would not be pursued.

It was the latest twist in a series of stunning events that have brought the gravest threat so far to President Vladimir Putin’s grip on power amid the 16-month-old war in Ukraine.

WATCH: How the attempted rebellion in Russia could affect Putin’s war in Ukraine

Over the weekend, the Kremlin pledged not to prosecute Prigozhin and his fighters after he stopped the revolt on Saturday, even though Putin had branded them as traitors and authorities rushed to fortify Moscow’s defenses as the mutineers approached the capital.

The charge of mounting an armed mutiny is punishable by up to 20 years in prison. Prigozhin escaping prosecution poses a stark contrast to how the Kremlin has treated those staging anti-government protests in Russia, where many opposition figures have gotten long sentences in notoriously harsh penal colonies.