Italian energy group Eni has agreed to buy three solar power projects in Spain from renewable energy developer X-Elio as part of plans to expand its green business.

The plants have a total installed capacity of 140 megawatts (MW), Eni said, adding it was in talks with X-Elio to develop more renewable energy projects in the country to reach 1 gigawatts (GW) over the next five years.

Eni, which makes most of its core earnings from oil and gas, unveiled an ambitious clean-up drive of its business last year that includes hiking its renewable energy capacity to 5 GW by 2025 and more than 55 GW by 2050.

The company is due to update its strategy on Friday.

"This initiative greatly reinforces Eni's presence in the Spanish market ... and it complements the existing businesses already established in the region," Eni Chief Executive Claudio Descalzi said.

X-Elio has 250 MW of renewable capacity under construction in Spain and more than 1.5 GW under development.