Chile's government was scrambling yesterday to deliver aid to southern and central regions devastated by Saturday's powerful earthquake after 10,000 troops imposed an overnight curfew in the worst affected areas in an attempt to halt looting.

Firefighters combing through a crumpled block of flats in the southern city of Concepción, the nearest to the epicentre of the 8.8 magnitude quake, said they had heard knocks from what they believed were three survivors trapped in the rubble of their apartment. As many as 50 people are believed still to be stuck in the ruins.

The official death toll rose to 711 but President Michelle Bachelet warned it was sure to climb further as the sheer magnitude of the devastation emerged.

The rebuilding effort could cost as much as $30bn (€22bn, £20bn), equivalent to about 15 per cent of Chile's gross domestic product, according to Eqecat, a company that helps insurers estimate catastrophe risks.

The earthquake sparked an early jump in copper prices as several mines were closed temporarily because of power outages in what is the world's top copper-producing nation. The mines had now resumed production and the bulk of the mining industry, centred in northern Chile, was spared by the earthquake.

Andrés Velasco, Chile's finance minister, told the Financial Times the government expected to be able to draw enough cash from the 2010 budget, which set aside $40bn for spending this year, to cover the emergency relief effort.

But he said Chile was sound fiscally. “We are a country with very small debt, just 6 per cent of gross domestic product . . . and we were only looking at a budget deficit of 1.1 per cent of GDP for 2010,” he said. In addition, Chile has $16bn in savings from when copper prices were very high.