SEOUL - Tens of thousands of workers held a demonstration here Saturday to protest against a government plan they say is aimed at weakening unionism, witnesses said.

The protestors from the Federation of Korean Trade Unions (FKTU) chanted slogans and waved banners, accusing the conservative government of President Lee Myung-Bak of seeking to destroy trade unions.

A National Police Agency spokesman estimated the crowd at 60,000 people.

They marched near the National Assembly, holding a large banner which read, "Let's save the trade union movement through general strikes."

Thousands of riot police were deployed but there were no immediate reports of violence.

The Labour Ministry wants to revise labour laws next year to allow multiple unions for each workplace and to prohibit wages for union representatives who spend most of their company time on union work.

FKTU, South Korea's largest labour union, with 700,000 members nationwide, has said it would hold a general strike in December unless the government withdraws its plans to revise the labour laws.