A leading US maker of advanced military surveillance drones announced Wednesday that it was willing to sell two to Ukraine for just $1, and called on the US government to approve the deal.

General Atomic Aeronautical Systems said it had been urging Washington for months to provide Ukraine its powerful Grey Eagle and Reaper drones, which US forces have used to great effect in surveillance and targeted attacks over Afghanistan, Syria, Iraq and other conflict zones.

It said the drones, which can fly long distances at mid-altitudes, are one of the most obvious, force-enhancing technologies that Ukraine needs in its war against Russian forces.

The US military has provided Ukraine with a number of small attack and surveillance drones, but nothing with the advanced technologies and long-range abilities like General Atomic's unmanned aircraft.

"From the outset of the Russian invasion, we began looking for options to respond to the requests of Ukrainian forces with our products, including the MQ-9 Reaper and MQ-1C Gray Eagle," General Atomics chief executive Linden Blue said in a statement.

He said the company has offered to train Ukrainian operators at no cost to the US or Ukrainian governments.

And the company was ready to hand over two of its own training aircraft, along with a ground control station and other hardware, for a symbolic $1.

Ukraine or someone else would have to pay for outfitting and transferring the aircraft and setting up the operation to put them in the air over the battlefield, he said.

"The offer is a remarkable deal with no strings attached," Blue said.

"All that is required is approval from the US government."

"From our perspective, it is long past time to enable Ukrainian forces with the information dominance required to win this war," he said.

Strike on residential building leaves 3 dead in Kramatorsk

At least three people were killed Wednesday and 20 wounded when a Russian rocket struck a residential building in the centre of the eastern city of Kramatorsk, Ukrainian officials said.

AFP saw two bodies at the scene as rescue workers cleared the rubble.

"Two hours ago, the Russian occupiers hit a residential building in the centre of the city with a rocket and completely destroyed it," regional governor Pavlo Kyrylenko said on the Telegram messaging app.

The regional police said on their official website that it was "preliminarily known that there are three dead civilians and 20 wounded".

"Peaceful people died and are under the rubble," Ukrainian President Volodymyr Zelensky wrote after the rocket strike.

"This is the daily reality of life in our country."

Kramatorsk is located in the eastern industrial region of Donetsk, parts of which, including its largest city, have been controlled by Kremlin-backed separatists since 2014.

Moscow is seeking to capture the entire region after declaring it part of Russia last year.