Ukrainian President Volodymyr Zelensky has publicly acknowledged for the first time that his troops are active in Russia's Belgorod region, which borders Ukraine.

"We continue to carry out active operations in the border areas on enemy territory, and that is absolutely just - war must return to where it came from," he said on Monday.

His comments also referred to Russia's Kursk region, where Ukraine still holds a small area after a major offensive last year. Moscow has since retaken most of the territory.

Zelensky said "the main objective" was to protect Ukraine's Sumy and Kharkiv border regions, and to "ease the pressure" on other parts of the vast front line, particularly in the eastern Donetsk region.

Russia's military had last month reported Ukrainian attempts to cross over into the Belgorod region - but said such attacks had been rebuffed. The areas in question are only a short distance inside Russian territory.

Russian President Vladimir Putin launched a full-scale invasion of Ukraine in 2022, and Moscow currently controls about 20% of Ukraine's territory.

The Kremlin has rejected US and European allegations that it is dragging its feet on US President Donald Trump's push for a ceasefire in the war.

Trump told reporters late on Monday that he was "not happy about what's going on", accusing Russia of "bombing like crazy right now". Zelensky's home city of Kryvyi Rih held funerals earlier for 20 people, including nine children, who were killed in a Russian missile attack last Friday.

In his video address late on Monday, Zelensky said he had been briefed by his top commander Gen Oleksandr Syrskyi about the situation on the front, "including our presence in the Kursk and Belgorod regions".

Zelensky thanked several army units defending Ukraine, including the 225th Assault Regiment deployed in the Belgorod region.

"Well done, guys! I'm proud of each and every one who is fighting for Ukraine!" the president said.

He provided no further details. It is his first explicit acknowledgement of Ukrainian troops in Belgorod.

On 18 March, Zelensky had indirectly confirmed that Ukrainian troops were there.

"There is an operation there," he said when asked by reporters to comment on a Russian defence ministry statement that Ukrainian troops had unsuccessfully tried to enter the western part of the Belgorod region.

Russia had said that all Ukrainian attempts to advance towards the villages of Demidovka and Prilesye had been rebuffed, and a cross-border raid had been prevented.

However, several Russian military bloggers at the time reported fighting in Demidovka itself, which lies about two kilometres (1.2 miles) from the Ukrainian border.

The US-based Institute for the Study of War (ISW) had also said in an update on 21 March that "Ukrainian forces recently advanced in Belgorod".

"Russian milbloggers claimed that Ukrainian forces advanced and are consolidating positions on the outskirts of Demidovka and Prilesye," the ISW said, adding that such claims were unconfirmed.

In the past two days, Russian military bloggers had reported that Ukrainian forces were withdrawing from the Demidovka area.

Ukraine's operation in Belgorod is believed to be on a much smaller scale compared to its actions in Kursk, where Kyiv at one point seized a number of villages including the regional town of Sudzha.

Zelensky and his top commanders have repeatedly said that such incursions have forced Moscow to redeploy troops from the Donetsk region, where Russian troops have been making steady - although slow - advances in recent months.

Ukraine could also be hoping to exchange the Russian areas it holds for parts of Ukrainian regions occupied by Moscow in any future peace negotiations that are being pushed for by the US.

A number of war analysts - both in Ukraine and the West - have questioned the military expedience of Kyiv's operations on Russian soil, pointing to reported high combat casualties and weapons supply difficulties.