Ukraine has retaken six villages that Russia captured in a recent push, the Ukrainian General Staff said, after Moscow made a swift advance in the east of the country.
On Tuesday, Russian forces pushed towards the town of Dobropillia.
"The advance of the enemy was stopped by the forces of the 1st Corps of the National Guard of Ukraine, together with adjacent and subordinate units, over the past three days," the General Staff said.
It added that six villages in the area were retaken.
The Russian army's gains were the biggest for a single 24-hour period in over a year, according to an analysis of data from the US-based Institute for the Study of War.
Ukrainian authorities ordered the evacuation of families with children from Dobropillia last month.
The town, which had a pre-conflict population of around 28,000, is under constant Russian drone and shell fire.
Ukraine targets Russian oil refinery, cargo ship
Ukrainian drones hit a Russian oil refinery overnight in the central city of Syzran, 800km behind the frontline, according to Ukraine's military.
It said that an apartment block was also targeted. Officials in Russia said that one person was killed.
Ukraine has targeted Russia's oil depots and refineries in long-range drone attacks in what it calls retaliatory strikes for Moscow's nightly barrages of its cities and its energy grid.
"The Syzran oil refinery in the Samara region of Russia, one of the largest in the Rosneft system, was hit," Ukraine's general staff said, referring to the network of facilities owned by Russian state-run energy firm Rosneft.
It said the facility produced aviation fuel and supplied the Russian army.
Unverified images on social media showed multiple fires and grey smoke billowing from the site.
Kyiv also said its forces had hit a cargo ship carrying drone components in Russia's southern Astrakhan region yesterday.
Russian officials confirmed that a vessel was damaged and said that no one was hurt in the attack.
Unverified images on social media showed a large cargo ship partially submerged.
A separate Ukrainian drone strike on an apartment block in the Russian border region of Kursk killed one person and wounded ten others, Russian officials said.
"Unfortunately, a 45-year-old woman died on the spot," Governor Alexander Khinshtein said in a video on Telegram, standing in front of a blown-out window.
Russian attacks also continued, with Ukrainian officials in the frontline Kharkiv and Donetsk regions reporting six civilians killed in strikes over the last 24 hours.
Ukraine has previously vowed to step-up its long-range strikes against Russia as Moscow launched record numbers of missiles and drones at Ukraine in recent months.
Russia's army said that Ukraine fired 53 drones overnight, while the Ukrainian air force said that Moscow launched 97.
Accreditation AFP/Reuters
