LONDON (Bloomberg) — Bermuda-based Frontline Ltd., the world's biggest operator of supertankers, posted first-quarter profit that beat some analysts' estimates as strengthening oil demand lifted charter income for the carriers.

Net income advanced to $79.7 million, or $1.02 a share, from $76.6 million, or 98 cents, a year earlier, Frontline said in a statement on Friday. It was expected to make $61 million, according to the median estimate of 13 analysts surveyed by Bloomberg.

Frontline expects "good results" in the second quarter, based on trading so far, the company said.

The Organisation of Petroleum Exporting Countries has raised output in 11 of the past 13 months, according to Bloomberg estimates. This month's 18 percent slide in oil prices may prompt the group to enforce output quotas more strictly, Robert Montefusco, a broker with Sucden Financial Ltd., said yesterday. That would reduce the flow of cargoes.

Frontline's very large crude carriers, designed to ship 2 million-barrel cargoes, made an average of $45,300 a day in the quarter. Its suezmaxes, half the size, earned $31,800 a day. Sales declined 6.9 percent to $331.8 million.

Overseas Shipholding Group Inc.'s VLCCs earned $49,818 a day, according to Bloomberg calculations based on the company's first-quarter earnings statement. Euronav NV, Belgium's largest owner of the vessels, made $49,000 a day from the ships.

The International Energy Agency cut its 2010 estimate for world oil demand to 28.7 million barrels a day this month, 400,000 barrels a day fewer than it estimated in April.

The supply of ships is being curtailed by Iran deploying its fleet to store heavy crude-oil cargoes that it can't sell, said Anders Karlsen, an analyst at Nordea Securities in Oslo. Demand for the vessels is being buoyed by China and other Asian economies, he said.