Estonia will close all its border crossings with Russia from 1 December after a suspected sabotage attack on a drone maker in the Baltic state over the weekend, which authorities said was ordered by Russia’s GRU military intelligence service.

On Saturday morning, eight people were detained during an attempted attack on Threod Systems, a defence company that manufactures long-range attack and reconnaissance drones. No injuries or damage were reported after the company’s security team responded to the incident.

Estonia’s internal security service, Kapo, said on Sunday the attack was carried out “with the aim of causing an explosion and setting the building on fire”. Authorities have requested a court order for five of those detained to remain in custody, Estonia’s public broadcaster ERR reported.

The Estonian prime minister, Kristen Michal, said the border closure was needed to reduce the risk of further attacks and “send a clear message that attacks on Estonia’s defence industry and defence capabilities” were unacceptable.

He linked the attacks with Estonia’s continuing support for Ukraine. “Russia’s aim is to make us afraid, make us hesitate and weaken our support for Ukraine. Estonia’s response is the opposite. We will strengthen our security, work even more closely with businesses and our allies, increase pressure on Russia and continue supporting Ukraine,” Michal said.

The Estonian foreign minister, Margus Tsahkna, echoed the warning, saying: “Russia must understand that hostile actions against Estonia come with consequences. Attempts to intimidate, destabilise, or undermine our security will not go unanswered.”

Estonia operates three border crossings with Russia – Narva in the north, and Koidula and Luhamaa in the south. The authorities did not specify how long the closure would be.

It is the second attempted attack on an Estonian defence firm that authorities have attributed to Russia, following an arson attack at Milrem Robotics in August.

In September, Kapo said it was confident that incident was “a deliberate and pre-planned attack carried out on behalf of Russian special services”. The agency also said it fitted a pattern of Russian attacks targeting defence and drone companies, particularly those with links to Ukraine.

At the time Estonia summoned Russia’s chargé d’affaires over the attack, but the Kremlin denied any link to Russia, saying it was a “baseless” and “ill-considered” accusation “with absolutely no relation to reality”.

Several European intelligence services have repeatedly warned of potential attacks against defence companies and growing Russian attempts to recruit citizens in EU and Nato countries on messaging platforms online to carry out acts of sabotage.

Michal noted that the weekend’s arrests came after security agencies told the defence industry of potential risks. “We do not warn about these threats without reason. Preparedness matters, and this time it clearly paid off,” he said.