Russia fired an intercontinental ballistic missile during an attack on the Ukrainian city of Dnipro on Thursday, Kyiv's air force said, in what would be the first use in war of a weapon designed to deliver long-distance nuclear strikes.

The launch, if confirmed, highlights rapidly rising tensions in the 33-month-old war after Ukraine fired U.S. and British missiles at targets inside Russia this week despite warnings by Moscow that it would see such action as a major escalation.

The Ukrainian air force said the missile was fired from the Russian region of Astrakhan, more than 700 km (435 miles) from Dnipro in central-eastern Ukraine. It did not specify what kind of warhead the missile had or what type of missile it was. There was no suggestion it was nuclear-armed.

The RS-26 was first successfully tested in 2012, and is estimated to be 12 metres (40 ft) long and weigh 36 tons, according to the Centre for Strategic and International Studies (CSIS). It said the RS-26 can carry an 800-kg (1,765-pound)nuclear warhead.