The Kremlin said on Friday that the St Petersburg International Economic Forum had suffered from a "denial of service" cyberattack on its accreditation system, forcing Russian President Vladimir Putin to delay a scheduled address by one hour.

Kremlin spokesperson Dmitry Peskov said in a call with reporters that the cyberattack began Thursday and disabled the forum's guest accreditation and admission system, leading to a host of problems with access.

He said specialists were working to fix the problem, and that Putin's keynote address had been moved back to 3 p.m. (1200 GMT).