Kiev, 10 June 2023 (dpa/MIA) - Several people have been injured and killed in the Ukrainian port city of Odessa during nighttime Russian drone attacks, the Ukrainian military said on Saturday.

Debris from a Russian attack drone shot down by air defences crashed into a multi-storey apartment building and started a fire, the Ukrainian army's southern operational command wrote on Facebook.

Three civilians were killed by the flames and 26 other people were injured.

The Ukrainian air force said separately that Russia had directed 35 drones and eight missiles at targets in Ukraine. Twenty Iranian Shahed drones and two ballistic missiles were shot down, it said.

In addition to Odessa, the Russian attacks were also directed against targets in the Poltava region and in Kharkiv.

Amid speculation about the possible start of Kiev's long-awaited major counteroffensive to retake territory from Russia, Britain said on Saturday it was recording increased military activity by Ukrainian forces.

There have been major Ukrainian military operations in the east and south of the country in the past 48 hours, the British Defence Ministry said on Saturday. In some areas, it said, Ukrainian forces had broken through Russian defence lines but were making making slower progress elsewhere.

In addition, the Defence Ministry said in its daily intelligence update that the Russian air force had been unusually active over southern Ukraine.

Russian President Vladimir Putin said on Friday that the Ukrainian counteroffensive had begun a few days ago. Kiev, however, is staying publicly mum and stressing that it won't comment on the start of its own offensive.

In his evening video address on Friday, Ukrainian President Volodymyr Zelensky spoke of "particularly difficult battles" under way in the 15-month-old war.