At least 15 people have been killed in Russian attacks on Ukraine, including 10 dead in ballistic missile strikes on an exhibition near Kyiv showcasing drone technology.

Ukrainian President Volodymyr Zelensky said some 100 people had been injured in the daytime attack on the exhibition, attended by prominent members of the defence sector.

Five people were also killed by Russian glide bombs in the eastern city of Sloviansk. Early on Saturday, military officials confirmed the deaths of two men in the northern city of Sumy.

On Friday evening, Zelensky said he had received intelligence that Russia was preparing another massive missile strike, which could happen “within the next 48 hours”.

A Ukrainian strike on Friday killed six people and wounded 26 in the Russian city of Kirov, more than 1,000km (600 miles) behind the front line. Ukraine also attacked warehouses of Wildberries – Russia’s biggest online retailer.

After the attacks near Kyiv, there were initially fears for the safety of Defence Ministry adviser Serhiy Beskrestnov, also known as Flash, and Lyuba Shypovych, who has been involved in developing technology for the Ukrainian army.

Following the incident, both took to social media to confirm they were unharmed, and Beskrestnov said he had stayed away from the event because of security concerns.

Ukrainian air force spokesman Yuri Ihnat told Ukrainian TV the attack involved three ballistic missiles, only one of which was intercepted.

Russia confirmed the attack. Its Defence Ministry said high-precision long-range weaponry had been used on a site where drones for use in targeting civil sites in Russia were being demonstrated.

It said producers of drones, as well as representatives of Ukraine’s drone forces and security services “directly planning and carrying out strikes on Russian territory” were present.

This is at least the third time since Russia’s full-scale invasion in 2022 that an exhibition of this kind has been hit.

There has been widespread outrage that a public event of this kind was being held at all and had, apparently, been widely advertised.

President Zelensky said the incident was being investigated, while Ukraine’s prosecutor-general said efforts were under way to establish who decided to hold the event and what safety measures were in place.