MOSCOW (Reuters) - President Vladimir Putin signed an executive order on Wednesday removing Russia's signature from the International Criminal Court's founding treaty, piling pressure on a court that is already reeling from withdrawals by some African countries.

Moscow never ratified the treaty, which it signed in 2000, meaning it never became a member subject to its jurisdiction. But the symbolic move coincided with the opening day of the general assembly of member states.

On Monday, the ICC angered Moscow by referring to Russia's 2014 annexation of Ukraine's Crimea as an armed conflict. It is also examining allegations of war crimes committed by Russian and Georgian forces during a brief 2008 war.

"Unfortunately, the court has not justified the hopes attached to it and has not become a genuinely independent authoritative organ of international justice," the Foreign Ministry said.

"It is revealing that in its 14 years of work the ICC has pronounced just four verdicts and spent over $1 billion."

Russia is under international pressure over its campaign of air strikes in Syria, with some human rights activists and U.S. officials accusing it of bombing civilians and civilian targets. Russia has denied those allegations.

Russia's announcement may be welcomed by African states like South Africa and Gambia, which have recently announced their withdrawals, but critics said the move was yet another example of Moscow flouting international norms.

"It confirms Russia's retreat from its international commitments," said Human Rights Watch activist Liz Evenson. "It's closing the door for people within Russia to this important judicial institution."

Kremlin spokesman Dmitry Peskov told reporters the decision to withdraw Russia's signature had been taken "in the national interest" and was a formality as it didn't change anything as far as jurisdiction was concerned.

Most African and European countries continue to support the court, the first permanent international war crimes tribunal. But many expect it to face increased diplomatic pressure from the United States under President-elect Donald Trump, who has promised a less internationalist foreign policy stance.

The ICC, based in The Hague, Netherlands, was founded when 120 countries adopted its founding treaty in 1998. It is seen as a successor to the Nuremburg trials after World War II and ad-hoc U.N. war crimes tribunals for the former Yugoslavia and Rwanda.

(Reporting by Andrew Osborn in Moscow and Stephanie van den Berg in The Hague; Editing by Christian Lowe)