KINSHASA - Thousands of local United Nations employees in Democratic Republic of Congo stopped work on Thursday to protest at pay and working conditions, hampering the world's largest peacekeeping operation.

Some 500 protestors blowing whistles and chanting slogans gathered in the capital Kinshasa outside the headquarters of the U.N. mission, MONUC, which employs some 7,000 local workers, many of them without contracts.

The strike grounded many U.N. transport flights across the central African nation the size of Western Europe, which is struggling to recover from a 1998-2003 war which killed nearly 4 million people, mainly from hunger and disease.

Union officials said the stoppage would continue until their demands were met regarding wages, grading and some other benefits.

"Since 1999 when MONUC was founded, many Congolese workers have not received the smallest promotion and their salaries have remained the same," said Guershom Nondo, president of the union delegation of Congolese MONUC workers.

One Congolese worker, who asked not to be identified, said that a local employee might receive $650 for a job for which a similarly qualified foreigner would be paid $7,500.

"Our expatriate colleagues treat us with disdain, some of them to the extent that they forbid us to use the toilets ... reserved for international staff," said the employee.

MONUC senior officials met for talks with the union delegation on Thursday, in the company of some foreign ambassadors.

A MONUC statement expressed optimism the talks would lead to the successful resolution of the strike, but it said some of the issues raised would need to be resolved by the international U.N. system.