Ukraine’s president has said North Korean forces have returned to the front line in Russia’s western Kursk region, after reports they had recently been withdrawn due to heavy casualties.

In a video address on Friday, Volodymyr Zelensky said the Russian army had “brought back in North Korean soldiers” who were carrying out “new assaults” in the region partially occupied by Ukraine.

He added “hundreds of Russian and North Korean military” personnel had been “destroyed”.

In January, Western officials told the BBC they believed at least 1,000 of the 11,000 troops sent from North Korea had been killed in the past three months. North Korea and Russia have not commented.

Russian President Vladimir Putin launched a full-scale invasion of Ukraine in February 2022.

Last week, Ukrainian special forces fighting in Kursk told the BBC they had not seen any North Korean troops there for the past 21 days.

A spokesman said it was probable they had been pulled out after suffering heavy combat losses.

The spokesman added that he was only referring to areas where his forces were fighting, without giving any details about how long that front line was.

Recent reports attributed to South Korean intelligence have suggested the North Koreans soldiers are unprepared for modern warfare, and are especially vulnerable to Ukrainian drones.

Military experts say the reports of North Korean casualties, if they continue at this pace, are unsustainable.

The soldiers were deployed after Russian President Vladimir Putin and North Koream leader Kim Jong Un deepened bilateral ties in recent months, including signing a security and defence treaty.

Pyongyang’s assistance to Moscow now also extends to large amounts of ammunition and weapons.

Ukrainian troops launched a lightning offensive in Kursk six months ago, seizing more than 1,000 sq km (386 sq miles) of Russian territory.

Since then, Russian forces have managed to retake a sizeable chunk of the region.

However, both Ukrainian and Russian military bloggers have reported in the past two days a new push by Ukrainian troops in Kursk.

Russia’s military has said the attacks have been repelled, but some reports suggest the Ukrainians have managed to seize more Russian territory. These have not been independently verified.

In other key developments on Friday:

• Russia’s military said its forces captured a key town of Toretsk in Ukraine’s eastern Donetsk region – but a Ukrainian military spokesman said fighting was continuing in the industrial hub
• US President Donald Trump said he would “probably be meeting President Zelensky next week, and I will probably be talking to President Putin. I’d like to see that war end”.