The National Cyber Security Centre said the distributed denial-of-service (DDoS) attacks, which make websites or network resources unavailable by flooding them with malicious traffic, resulted in minor outages.

"A first DDoS attack on various federal government websites and organisations involved in the summit on peace in Ukraine began this morning," the NCSC said.

"The attacks were expected and are presumed to be in connection with the summit. They resulted in minor outages... The operation of the affected units was not significantly affected."

The NCSC said it would issue regular updates.

"The DDoS attacks are intended to impact the availability of websites. The security of data and systems was never at risk. Hacktivists use such cyberattacks to launch disruptive manoeuvres in cyberspace to spread political messages and attract attention," it said.

"The attacks are within the expected range and there is currently no acute danger."

On Saturday and Sunday, Switzerland will host the first Summit on Peace in Ukraine, at the luxury Burgenstock resort outside Lucerne.

The Swiss government says dozens of countries have confirmed their participation.

The summit will try to come up with a roadmap for involving both Ukraine and Russia in a future peace process.

Russia started its full-scale invasion of Ukraine in February 2022. Moscow said it was not interested in attending the conference and therefore was not invited.