* Court bans planned Hellenic Petroleum strike
* 10-day walkout was planned to start May 6
* Decision strengthens management's hand in wage talks
* Workers consulting lawyer on next steps (Adds detail, labour union reaction)
ATHENS, May 5 (Reuters) - A Greek court on Thursday banned a planned strike at the country's biggest oil refinery Hellenic Petroleum, weakening workers' hand in wage talks with management.
Workers were planning to start a 10-day walkout on Friday, their second in a month, to protest against management plans to extend working hours and link pay to productivity.
The previous walkout, held in April, had led to a shutdown of the company's three refineries, which account for about two thirds of the Greece's total refining capacity.
"An Athens court of first instance ruled today that the 10-day strike declared by the (labour union) PSEEP is ... illegal and as such cannot be held," Hellenic said in a statement.
Hellenic's labour union will consult with its lawyer to decide what to do next, its chief Panagiotis Ofthalmides told Reuters.
Hellenic's labour union and management have been holding wage talks for months. Workers demand wage increases in line with euro zone inflation. Management accepts this on condition that part of their pay be linked to productivity, with the working week extended to 40 hours. (Reporting by Harry Papachristou. Editing by Jane Merriman)