ISLAMABAD - The Taliban insurgency claimed Friday that U.S. airstrikes killed 16 of its fighters in eastern Afghanistan who were battling militants loyal to the rival Islamic State.

A Taliban spokesman, Zabihullah Mujahid, asserted Friday that Taliban fighters were carrying out attacks against Islamic State bases in eastern provinces of Nangarhar and Kunar, when they came under fire by U.S. drones. He said the U.S. repeatedly bombed "our positions, vehicles and defense lines” and inflicted casualties on the Taliban fighters.

The Pentagon has not commented on the claim.

The accusations came a day after Russia alleged “unidentified” helicopters were ferrying ammunition and arms to Islamic State fighters in a northern province of Afghanistan and demanded explanations from local as well as their NATO-led foreign military partners.

On Thursday, the Russian Foreign Ministry spokesperson said that “unidentified” helicopters are conducting military missions in support of terrorists linked to the Islamic State faction in the northern Afghan province of Sar-e-Pul.

“We note that this is happening in the direct vicinity of Central Asian states’ borders and many ISIS (Islamic State) militants in Afghanistan hail from these countries,” said Maria Zakharova.

She said that Moscow was awaiting a reaction from Afghan security agencies and the U.S.-led international forces deployed in the country.

U.S. Army from NATO and Afghan commando forces are FILE - U.S. Army and Afghan commando forces are seen at a checkpoint during a patrol against Islamic State militants, at Deh Bala district in the eastern Afghan province of Nangarhar, July 7, 2018. FILE - U.S. Army and Afghan commando forces are seen at a checkpoint during a patrol against Islamic State militants, at Deh Bala district in the eastern Afghan province of Nangarhar, July 7, 2018.

The Taliban and Russia have accused the U.S. military of helping Islamic State fighters in the past, charges that Washington has rejected as "completely untrue." Former Afghan president Hamid Karzai first suggested in 2009 that the United States was secretly helping the Taliban in an effort to prolong the war. The allegation came at a time of fraying relations between Karzai's government and Washington, and U.S. officials have long said there is no basis for the claim.

U.S. officials have also criticized Moscow for maintaining ties with the Taliban on the pretext of fighting terrorist groups in Afghanistan, saying Moscow's policy undermines international gains in the war-shattered country.

Moscow conference on Afghanistan

Meanwhile, Russian officials have urged Kabul to attend next month’s multi-nation consultative conference in Moscow on the future of Afghanistan, where Taliban envoys will also be in attendance.

The Afghan government has refused to participate in the meeting unless Taliban negotiators agree to direct bilateral talks with its delegates on the sidelines of the September 4 gathering in the Russian capital.

In a statement issued Thursday, the Russian Foreign Ministry defended the event as an important step toward a comprehensive Afghan settlement.

“The purpose of inviting Taliban representatives to the Moscow meeting is to deliver a collective appeal to restore peace in Afghanistan directly to the armed Afghan opposition.… We expect representatives of Kabul to take part in the Moscow format meeting,” it said.

Washington has also declined an invitation to attend the Moscow conference because U.S. officials maintain any peace and reconciliation effort will have to be led by the Afghan government.

VOA national security correspondent Jeff Seldin contributed to this report.