CAIRO -- The U.S. military Tuesday accused Russia of deploying fighter planes to conflict-stricken Libya to support Russian mercenaries aiding east-based forces in their offensive on the capital, Tripoli.

Russia called the claim "disinformation."

In a strongly worded statement, the U.S. Africa Command said the Russian military aircraft arrived in Libya recently from an airbase in Russia via Syria, where they were repainted to hide their Russian origin. AFRICOM did not say how many aircraft were transferred or when exactly they arrived in Libya.

"For too long, Russia has denied the full extent of its involvement in the ongoing Libyan conflict. Well, there is no denying it now. We watched as Russia flew fourth generation jet fighters to Libya -- every step of the way," said U.S. Army Gen. Stephen Townsend, commander of the U.S. Africa Command.

Andrei Krasov, deputy head of the defence committee in the lower house of Russia's parliament, rejected the U.S. claim as "disinformation." "It's another attempt by the U.S. to play the Russian card," he said, according to the Interfax news agency.

AFRICOM said the aircraft were likely to provide close air support and offensive fire for the Wagner Group, a Russia-based state-sponsored company that employs mercenaries to fight alongside the eastern forces of military commander Khalifa Hifter.

Libya was plunged into chaos when a NATO-backed uprising toppled longtime dictator Moammar Gadhafi in 2011. The country is now split between a government in the east allied with Hifter and one in Tripoli, in the west, supported by the United Nations.

Hifter's self-styled Libyan Arab Armed Forces launched an offensive to capture Tripoli last year, clashing with an array of militias loosely allied with the U.N.-supported but weak government there. Hifter is backed by The United Arab Emirates, Egypt and Russia, while the Tripoli-allied militias are aided by Turkey, Qatar and Italy.

In the past two months, Hifter's forces have lost a string of western towns and a key airbase after Turkey stepped up military support for his rivals, sending drones, air defence systems, armoured vehicles and thousands of Syrian mercenaries.

However, he said Saturday his forces would continue fighting and they stepped up airstrikes on Tripoli and its outskirts. The LAAF said Friday they were able to repair four fighter jets to return them to action, without saying what kind of aircraft. It said they had been grounded for some time, without elaborating.

Townsend said neither Hifter's LAAF nor private military companies "can arm, operate and sustain these fighters without state support -- support they are getting from Russia."

Russia has employed state-sponsored Wagner in Libya to conceal its direct role and to afford Moscow plausible deniability of its malign actions, AFRICOM said.

"The world heard Mr. Hifter declare he was about to unleash a new air campaign. That will be Russian mercenary pilots flying Russian-supplied aircraft to bomb Libyans," Townsend said.

Acting U.N. special envoy Stephanie Williams warned last week that the war in the North African country will "intensify, broaden and deepen" because of increasing foreign intervention and the influx of weapons, military equipment and mercenaries to both sides.

In a phone call with Libya's parliament speaker Aguila Saleh on Tuesday, Russian Foreign Minister Sergei Lavrov said attempts to resolve the Libyan crisis by force are futile "and that there is a need for the immediate launch of constructive dialogue involving all Libyan political forces," according to a statement by Russia's Foreign Ministry.

Associated Press writer Vladimir Isachenkov in Moscow contributed.