By Damian Grammaticas BBC correspondent in Hong Kong

It was the biggest protest for years (AP)

Tens of thousands of farmers and fisherman have marched through the Taiwanese capital, Taipei, in the largest protest on the island since President Chen Shui-bian took office two years ago.

They were demonstrating against government attempts to reform debt-laden agricultural credit unions that loan money to the farmers and fishermen.

According to the city's police, 100,000 farmers and fishermen took part.

Some carried sheaves of wheat. Others had banners saying, "If farming dies, the nation dies".

They marched to the presidential office which was surrounded by barbed wire barricades and riot police. The leaders of Taiwan's two main opposition parties joined the protesters.

Protesters marched to the presidential palace, but later dispersed peacefully

Since Taiwan joined the World Trade Organisation earlier this year, it has had to open its agricultural sector to cheap imports.

Many farmers are struggling. In August, the government began reforming the credit co-operatives that lend money to the agricultural sector.

It placed limits on the amount they could lend because, it says, they are saddled with debts and are costing Taiwanese taxpayers $1m a day.

The weight of opposition forced the government to postpone some of the reforms last Monday.

As a result, the finance minister and the prime minister both offered to resign but their resignations were not accepted. President Chen has seen his approval ratings fall to an all time low of 36%.