BUENOS AIRES, March 24, 2008 (AFP) - Thousands of people demanded speedier trials for human rights abusers on the 32nd anniversary Monday of the military coup that launched the 'dirty war,' as a 12-day farmer protest over a soya tax hike got nastier.

'Thirty years waiting for justice is shameful,' said Estela Barnes, one of thousands who protested in Buenos Aires against the slow pace of trials against the leaders of the military junta blamed for 30,000 people killed and missing from 1976-1983.

'The trials we've been fighting for for 30 years are starting to come true, but it's way too slow and people aren't getting justice,' said a street-wide banner signed by 300 social, political, cultural and religious groups.

Nearly two dozen people have been indicted and are awaiting trial on torture and murder charges related to the military junta's crackdown against political dissidents and left-wing groups, but hundreds more are reportedly going unpunished.

Meanwhile, a nationwide protest by farmers against a tax hike on soya exports entered its 13th day Monday with no end in sight, as Justice Minister Anibal Fernandez said the government would not give in to demands to roll back the measure.

'The government has decided it will not negotiate under pressure, as we are right now,' he told reporters a day before leading farmer unions and groups are to meet to decide the next step in their protest.

The 12-day protest has led to clashes and some injuries as farmers squared off with truck drivers around the country -- tractors were stopping trucks loaded with produce from reaching their markets, while teamsters blocked roads under the byword: 'If we can't get through, nobody gets through.'

The government imposed the tax hike on soya exports as a way of raising extra revenue on the back of the worldwide demand for commodities which has seen the price for the beans skyrocket 70 percent in the last year.

The tax is to be calculated using international prices as the reference.

Half of Argentina's farmland is given over to growing the profitable plant, which is now the country's main export.