Swedish shipping companies were told to exercise the same vigilance when they set sail in the Baltic Sea as they would off the coast of Somalia after the Maltese- flagged freighter Arctic Sea was hijacked off Sweden last month.

The Swedish Shipowners' Association told its members that while the July 24 hijacking was probably an isolated incident, such events could create an "epidemic effect" by inspiring copycat attacks, Tryggve Ahlman, head of security at the Gothenburg, Sweden-based association, said by telephone today.

"We've talked with the companies that are active in these waters," Ahlman said. "They've come to us with questions and it's only natural that they increase their readiness. The procedures they have in the Gulf of Aden should be observed everywhere."

Pirates seized 28 ships in the Gulf of Aden off Somalia in the year to Aug. 10, according to the U.S. Navy. After the release of the Italian-owned Buccaneer earlier this month, they were holding eight ships and at least 163 seamen, according to Ecoterra, an environmental group that monitors Somali piracy.

Sweden has provided warships and soldiers to the European Union's anti-piracy operation, Atalanta, in the Gulf of Aden.

The Russian navy located the Arctic Sea, operated by Helsinki-based Oy Solchart Management AB, on Aug. 17 near the Cape Verde islands off west Africa, detaining eight suspected hijackers.

Ransom demand

The armed group had boarded the freighter off Sweden on July 24, then forced the crew to change course toward Africa and turn off the navigational equipment, Russian Defense Minister Anatoly Serdyukov said. The ship, with a crew of 15 Russian sailors, had been en route from Finland to Algeria.

The hijackers demanded a ransom of US$1.5 million from the ship's insurer, Renaissance Insurance, Vladimir Dushin, the company's vice president for security, said yesterday. Renaissance received a call on Aug. 3 from a person speaking English and claiming to be an intermediary for the hijackers, Dushin said.

Russia's Defense Ministry today confirmed that a ransom demand had been made, and that the hijackers threatened to blow up the boat if it wasn't paid, Interfax reported.

The Arctic Sea's 25-day odyssey sparked a wave of international speculation about its fate, including a reported sighting at the Spanish port of San Sebastian and a possible second attack off Portugal.

Submarine fleet

Swedes were shocked by the attack in their waters, since hijackings have been unknown off the country's coast since the 17th and 18th centuries, Ahlman said.

Rossiyskaya Gazeta, the Russian government's newspaper of record, reported yesterday that the 98-meter (322-foot) Arctic Sea was steered to the Cape Verde area because the waters there are difficult for submarines to navigate.