LONDON (Bloomberg) — Bermuda-based Frontline Ltd., the world's biggest oil-tanker company by market value, said first-quarter profit climbed after Opec pumped a record amount of crude, increasing demand for shipping.

Net income climbed to $221 million, or $2.95 a share, from $158.8 million, or $2.12, a year earlier, Frontline said yesterday in a statement distributed by Hugin. Sales gained 53 percent to $528 million as ship-rental rates advanced.

The tanker market has "improved considerably" in the current quarter because refineries are building crude stocks and ships are making longer voyages to deliver oil, Frontline said. Iran is using as many as 20 supertankers as floating storage, further crimping fleet supply, tanker-tracking company PetroLogistics Ltd. said yesterday.

Tanker-rental rates posted their biggest two-month gain in at least 16 years in November and December as the Organisation of Petroleum Exporting Countries shipped record amounts of oil. A month to six weeks elapses between the hiring of a tanker and the first rental payments from oil companies.

Frontline climbed 1.50 kroner, or 0.4 percent, to 341.50 kroner as of 9.09 a.m. in Oslo trading. The stock has advanced 32 percent this year.

Record shipments of crude oil from Angola to China boosted average voyage lengths. Fleet expansion was also curtailed because ship owners paid to convert tankers into iron-ore transporters, a market that's posting record earnings.

Frontline's largest ships, very large crude carriers, or VLCCs, are able to haul about two million barrels of crude. These vessels made the shipping line $82,400 a day compared with $49,900 a year ago.

Ships half the size, known as suezmaxes because they're the biggest that can sail through Egypt's Suez Canal fully loaded, made $51,600 compared with $34,900 last year.

VLCCs operated by Euronav NV, Belgium's only publicly traded oil-tanker owner, made $100,000 a day in the first quarter. The Antwerp-based company's suezmaxes earned $51,000 a day.

Frontline's profit was boosted by $37 million after an affiliated company sold a ship and Frontline sold shares of a unit. The median of nine analyst estimates was for net income of $175.6 million after asset sales, and $191.6 million before asset sales.

Opec pumped record amounts of crude every month from September to February, according to data compiled by Bloomberg.