Marubeni, a Japanese investment firm, announced that they have signed an agreement to acquire a 25% stake in Ireland-based Mainstream Renewable Power group for EUR100 million. Analysts said the deal is another indication that international interest in Europe's green energy sector has been on the rise.

The deal is the largest transaction for Mainstream and is also considered one of the largest equity investments in an independent renewables firm in recent times. Mainstream is currently constructing more than 40 wind and solar parks around the world.

"It will allow us to be the leader in this once-off transition to renewable energy," Eddie O'Connor, chief executive of Mainstream, said.

Marubeni has a significant presence in the global oil and gas sector. The company, however, is ramping up its renewable energy ventures in many countries, especially in the offshore wind industry.

"We think the offshore wind market is expanding all over the world," said Marubeni Europower president, Hiroshi Tachigami.