More than 200 people were feared killed today and many others injured after a huge earthquake devastated the New Zealand city of Christchurch on what is being called the country’s ‘darkest day’.

Prime Minister John Key warned of a rising death toll and said: “This is a community in agony. We may be witnessing New Zealand’s darkest day.”

The lunchtime tremor caused widespread damage, bringing down high-rise office blocks, tearing up roads and wrecking two cathedrals.

The official death toll stands at 65, but at least 200 people are still believed to be trapped under rubble and frantic rescue efforts are now under way. By 2pm (GMT), 120 people had been pulled from wrecked buildings.

The Queen said she was “utterly shocked” by the disaster and sent ‘deep sympathy’ to the relatives of those who have been killed. David Cameron also sent his condolences and added:”Britain stands ready to provide whatever assistance is required.”

Residents, office workers and tourists were among the casualties in the 6.3-magnitude quake.

The three-mile deep tremor struck around six miles outside the city and is believed to be an aftershock from a 7.1-magnitude earthquake which struck last September. A state of emergency has been declared in the city. Both the Catholic and Anglican cathedrals were badly damaged, sending stone debris crashing onto the pavements below.

Office workers clung onto window ledges after the floors in their buildings collapsed, while others returned from lunch breaks to find their workplaces levelled by the force of the quake, with colleagues trapped in the rubble.

City Mayor Bob Parker said this afternoon: “This is a terrible, terrible toll on our city. There is no power in most of the city; there is no water.”

The quake caused a block of ice weighing 30 million tons to shear away from New Zealand’s biggest glacier, in Lake Tasman, causing huge waves.