Frontline advanced as much as 10.5 percent on Tuesday after the Norwegian company and its main owner took a 5.2 percent stake in Overseas Shipholding Group, boosting takeover speculation.
Chief Executive Bjoern Sjaastad declined to comment on Frontline's plans for its OSG holdings and stuck to the wording of Frontline's March 20 statement that the group was interested in talks with OSG to create shareholder value.
Frontline announced last week in a filing to U.S. regulators that it and firms directly controlled by its main shareholder, John Fredriksen, bought a 5.2 percent stake in OSG and a forward contract on 4.4 percent more.
Analysts and Norwegian media said Frontline and Fredriksen could be preparing a takeover offer for OSG, but Sjaastad would not confirm or deny that.
After setting a new four-week high of 239.75 crowns, Frontline shares cooled off to 232.50 crowns by 10.02 GMT, still up 7.1 percent and valuing Frontline at about $3.29 billion.
As of 2008, Frontline, based in Hamilton, Bermuda, is the world's largest oil tanker company. The company's fleet consists of 66 tankers; totaling 16.4 million dead weight tons. The company's largest shareholder is Hemen Holding Ltd., a company indirectly controlled by the chairman of Frontline, billionaire John Fredriksen, Norway's highest net worth person.
Overseas Shipholding Group Inc. is the second largest oil tanker company in the world.
OSG has offices in Athens, Houston, London, Manila, Newcastle, New York, Philadelphia, Quebec, Singapore and Tampa with nearly 4000 sea and shore-based employees.
OSG shares have risen 20 percent over the past week, and closed up 1.9 percent on Monday at $69.52.