Italian companies have signed deals worth more than 1 billion euros ($1.13 billion) with Russian firms at an economic forum in St. Petersburg, Italian Prime Minister Matteo Renzi said on Friday.

The accords, including some announced on Thursday, involved Italian companies in the construction, start-up financing, energy, electricity technology and infrastructure sectors.

"These are deals which are all legitimate within the context of the sanctions regime because we respect all the rules," Renzi told reporters. He said the accords "potentially open the way to deals worth between 4 and 5 billion euros".

The European Union imposed sanctions which apply mainly to some Russian banks and oil companies after Russia annexed Crimea from Ukraine in March 2014, and stepped them up as the Kremlin backed rebels in eastern Ukraine.

Renzi later repeated at a news conference that sanctions against Russia should not be renewed automatically.

Among the agreements announced on Friday was a joint venture between Italian shipbuilder Fincantieri and Rosneft. Oil services firm Saipem and Novatek struck a strategic partnership to work together on liquefied natural gas projects.

Italian state lender Cassa Depositi e Prestiti, Azerbaijani state petrol company Socar, Russian credit agency Exiar and Gazprombank signed a memorandum of understanding to build a petrochemical plant near Baku. ($1 = 0.8865 euros)