Iran’s foreign minister on Saturday for the first time acknowledged that his country had sent drones to Russia, according to the Iranian state news media, but said that the deliveries had all taken place before Moscow’s invasion of Ukraine in late February.

Russia has used Iranian-made drones in a series of deadly strikes that have wreaked havoc on Ukrainian cities, according to Ukrainian and Western officials.

Iran has denied sending drones to Russia for use in Ukraine, and the Kremlin has denied using Iranian drones to attack civilians. But international calls for accountability have mounted as deadly assaults in recent weeks helped debilitate Ukraine’s electricity supplies as the cold sets in.

The United States, the European Union and Britain have imposed new sanctions on Iran over the attack drones.

Iranian Foreign Minister Hossein Amir Amirabdollahian acknowledged in remarks carried by Iran’s state-run IRNA news agency that his country had sent drones to Russia. He did not specify the make or model of drones delivered to Moscow.

Amirabdollahian said the accusations from Western nations that Iran’s drones had been supplied for use in Russia’s war in Ukraine were false, since the deliveries took place months before the invasion, according to IRNA.

Iran also has sent trainers to Russian-occupied areas of Ukraine to help Russian fighters overcome problems with the drones, according to current and former U.S. officials. The moves underscore the close ties between Iran and Russia, particularly as the Kremlin has sought to offset its international isolation since starting the war.

Iran has officially said it would not provide either side of the conflict with military equipment but had confirmed that a drone deal with Russia was part of a military agreement that predated the invasion of Ukraine.

This article originally appeared in The New York Times.