OSLO (Reuters) - Norway's DNB, the country's largest bank, reported a better-than-expected net profit in the first quarter on Thursday as it wiped the slate clean of loan losses due to a pick-up in activity in the oil sector, the Nordic country's top industry.

While analysts in a Reuters poll had expected loan losses of 604 million crowns ($75.90 million) in the quarter, the bank recorded instead a net reversal of 330 million crowns.

DNB cited a number of successful restructurings in the Norwegian oil sector as one of the reasons. "Optimism is back in the oil sector," CEO Rune Bjerke said in a statement.

DNB reported a net profit of 5.7 billion crowns ($716.24 million) above expectations in a Reuters poll of analysts for 5.1 billion crowns.

The company also lowered its tax guidance for 2018 and 2019 to 20 percent of profits from a previous expectation it would have to pay 23 percent.

(Reporting by Gwladys Fouche, editing by Terje Solsvik)