Norway's annual offshore exploration licensing round in mature areas attracted bids from 21 petroleum firms, including Shell SHEL.L, Aker BP AKRBP.OL and Equinor EQNR.OL, the country's oil and energy ministry said on Friday.

"We need further exploration to make new discoveries which in turn pave the way for investments to maintain production," Energy Minister Terje Aasland said in a statement.

In May, the ministryoffered 37 new blocks to search for oil and gas in the Norwegian and the Barents Seas in its so-called pre-defined areas (APA) exploration round.

The annual predefined areas rounds of exploration acreage are central to Norway's strategy of extending its oil and gas production, a policy fiercely opposed by environmentalists.

Source: Reuters (Reporting by Stine Jacobsen, editing by Terje Solsvik)