Senior Polish officials were targeted in a cyber attack that originated in Russia, Poland’s de facto leader Jaroslaw Kaczynski said on Friday.

The claim comes two weeks after an account on the Telegram social media platform began leaking what it claimed were emails sent by government officials, including the top aide to prime minister Mateusz Morawiecki.

Kaczynski, the leader of the ruling Law and Justice party, alleged that “the most important Polish officials, ministers [and] MPs of various political groups” had been targeted in the attack, whose purpose was to “hit Polish society and destabilise our country”.

“The analysis of our [intelligence] services and the special services of our allies allows us to say clearly that the cyber attack was carried out from the territory of the Russian Federation,” he said.

“Its scale and scope are broad.”

Russia has repeatedly denied carrying out cyber attacks against western targets. However, in recent months the question of cyberwarfare has become an increasing irritant in relations between Moscow and the west.

Earlier this week, US president Joe Biden warned his Russian counterpart Vladimir Putin that certain critical infrastructure should be “off limits” from attacks, as the US and Russia agreed to hold talks on cyber security.

Putin’s spokesman Dmitry Peskov on Thursday denied that Biden had accused the Kremlin of being behind cyber attacks, but conceded that attacks could be taking place from Russian soil.

Meanwhile, Nato heads of state and government approved a cyber defence strategy and extended powers to invoke the western military alliance’s Article 5 principle of collective defence in cases of co-ordinated cyber attacks.

Kaczynski said Poland was still gathering evidence on the attack on its officials. The government briefed MPs on Wednesday during a sitting of parliament which was made secret at the request of the prime minister.

Michal Dworczyk, the top aide to Morawiecki, admitted last week that some information was stolen from mailboxes and social media accounts belonging to him and his family. But he also warned that some of the information that had been published was fabricated.

“At the moment I am not in a position to say precisely when my mailbox was broken into, but I would like to underscore that I did not use it to send any information which could pose a threat to state security,” he said.

“The goal [of such attacks] is spreading disinformation including by mixing true information with false information which has been fabricated on purpose for the needs of these sorts of activities.”

The attack on Dworczyk’s electronic communications follows a series of other alleged cyber attacks on figures linked to the ruling PiS party this year.

In January, Marek Suski, a senior PiS MP, said his Twitter account had been hacked after it posted pictures of a scantily clad political activist. He added that the attack could be an element of “hybrid warfare” directed against Poland.

Additional reporting by Henry Foy