KYIV, Ukraine, June 23, 2025 (AFP) - Ukraine said Monday "another massive attack" on Kyiv by Russian drones was underway, a day after the country's top military commander vowed to increase the "scale and depth" of strikes on Russia.

Diplomatic efforts to end the three-year war have stalled, with the last direct meeting between the two sides almost three weeks ago and no follow-up talks scheduled.

"Another massive attack on the capital. Possibly, several waves of enemy drones," said a statement from Tymur Tkachenko, head of Kyiv's military administration.

Two people were hospitalised in the Solomianski district, said Kyiv Mayor Vitali Klitschko, and two others were injured near a metro station in the Sviatochinski district, Tkachenko later said.

AFP journalists in Kyiv heard the buzzing of a drone flying over the city centre and explosions, as well as gunfire.

They saw around 10 people sheltering in the basement of a residential building in central Kyiv waiting for the attack to end, most of them scrolling their phones for news.

The latest strikes came after Ukrainian commander-in-chief Oleksandr Syrsky vowed to intensify strikes on Russia.

"We will not just sit in defence. Because this brings nothing and eventually leads to the fact that we still retreat, lose people and territories," he told reporters, including AFP.

Syrsky said Ukraine would continue its strikes on Russian military targets, which he said had proved "effective".

"Of course, we will continue. We will increase the scale and depth," he said.

- Fair response -
Ukraine has launched retaliatory strikes on Russia throughout the war, targeting energy and military infrastructure sometimes hundreds of kilometres from the front line.

Kyiv says the strikes are a fair response to deadly Russian attacks on Ukrainian infrastructure and civilians.

At least four people were killed in an overnight Russian strike on an apartment building in the eastern Ukrainian city of Kramatorsk, while a strike on a Ukrainian army training ground later in the day killed three others, officials said.

In wide-ranging remarks, Syrsky conceded that Russia had some advantages in drone warfare, particularly in making fibre-optic drones that are tethered and difficult to jam.

"Here, unfortunately, they have an advantage in both the number and range of their use," he said.

He also claimed that Ukraine still held 90 square kilometres (35 square miles) of territory in Russia's Kursk region, where Kyiv launched an audacious cross-border incursion last August.

"These are our pre-emptive actions in response to a possible enemy offensive," he said.

Russia said in April that it had gained full control of the Kursk region and denies that Kyiv has a presence there.

Russia occupies around a fifth of Ukraine and claims to have annexed four Ukrainian regions as its own since launching its invasion in 2022 -- in addition to Crimea, which it captured in 2014.

Kyiv has accused Moscow of deliberately sabotaging a peace deal to prolong its full-scale offensive on the country and to seize more territory.

The Russian army said Sunday that it had captured the village of Petrivske in Ukraine's northeast Kharkiv region.

Russian forces also sent at least 47 drones and fired three missiles towards Ukraine between late Saturday and early Sunday, the Ukrainian air force said.