ROME (Reuters) — Italian oil group Eni SpA is examining the sale of some assets in the North Sea, Chief Executive Paolo Scaroni said on Tuesday, a sale valued by a newspaper at more than $1 billion.

The sale would be part of a periodic portfolio clean-up by Eni, Europe's third-biggest oil company by market value, Scaroni said.

"We will see if there are opportunities to make sales. All the same it is a small affair, some thousands of barrels. We are examining (it)," he told reporters on the sidelines of a book presentation. Scaroni declined to give more details.

The Sunday Times newspaper reported Eni had hired Rothschild to sell the fields.

They produce about 20,000 barrels of oil a day and contain 120 million barrels of reserves.

Eni's daily oil and gas output fell 1 percent in the first quarter to 1.78 million barrels of oil equivalent.

The newspaper said the sale would be one of the largest in the North Sea in recent years and would be hotly contested by Japanese buyers.

It put potential bids at more than $1 billion.

The sale does not include Eni's stakes in the Liverpool Bay, J Block or Elgin fields, it said.