The hot mic moment came after Ukraine accused Russia of firing an intercontinental ballistic missile at the city of Dnipro, in what Russian military bloggers speculated was an attack on aerospace manufacturer Pivdenmash -- previously known as Yuzhmash.

"Masha," an unknown male voice on the phone said, addressing Zakharova using a diminutive form of her first name.

"On the 'Yuzhmash' ballistic missile strike that the Westerners have started talking about, we are not commenting at all," the voice added.

In later comments to Russian state news agency TASS, Zakharova said the phone call was aimed at clarifying whether the foreign ministry was able to broach a specific topic and dismissed any "intrigue".

"I clarified with experts whether this topic is ours. The answer came during the briefing -- the Foreign Ministry does not comment. So there is no intrigue," she told the news agency.

The Ukrainian air force said earlier Russia had launched several types of missiles at Dnipro in the morning, including an intercontinental ballistic missile for the first time since the conflict began.

An air force source told AFP it was "obvious" that the missile, which is designed to carry both conventional and nuclear warheads, did not carry a nuclear charge.