Hundreds of workers on Norwegian offshore oil and gas rigs went on strike on Tuesday after rejecting a proposed wage deal, leading to the shutdown of one Shell-operated field and helping send Brent crude prices higher.

"We haven't been contacted by the shipowners yet. They have to make the contact, they know our demands. Could be a strategic move from them to reach out before we shut more rigs on Sunday," Safe union leader Hilde-Marit Rysst told Reuters.

The union plans to have an additional 901 workers on strike from 2200 GMT on Sunday, unless the dispute is resolved.

Those employees work on exploration and production drilling rigs owned by Saipem, Transocean, Songa Offshore, Odfjell Drilling, Archer and COSL, among others.

Still, Sunday's possible escalation is not expected to lead to any further drops in output for now.

The Norwegian Shipowners' Association, representing employers, does not intend to initiate contact with Safe on Thursday, a spokeswoman said.

"We have no contacts planned today," she said. "What happens afterwards can change any minute."

The Shipowners' Association is in contact with all drillers involved to assess the situation.

Shell told Reuters it had completed the shutdown of the Knarr field, which had a daily output of 23,900 barrels of mostly oil, but also natural gas liquids and natural gas.

Equinor, Norway's largest oil and gas producer, reiterated that the strike had halted some of its drilling and well intervention operations, though the company's output remained unaffected.

"We will continue to evaluate what is happening and will monitor the situation," said a spokesman for Equinor, formerly known as Statoil.

One strike-hit rig, the Songa Enabler, is due to drill an exploration well in the Barents Sea for Equinor in August.

"At the moment, it (this strike) will not have any immediate effect on our exploration plans. Exploration in the Barents Sea is in late summer, it has not started yet," the Equinor spokesman said.

(Editing by Gwladys Fouche and Dale Hudson)

By Lefteris Karagiannopoulos