Breaking News: Christchurch, New Zealand rocked by two large earthquakes

Extensive damage has been reported after two major aftershocks in the New Zealand city within two hours.

Toby Manhire in Auckland guardian.co.uk
Earthquake topples Christchurch Cathedral's spire
The ChristChurch Cathedral spire, pictured after the February earthquake. Aftershocks are reported to have caused fresh damage Photograph: Mark Mitchell/AP

Reports of building collapses and live rescues were emerging on Monday afternoon after Christchurch was hit by two large aftershock, less than four months after the New Zealand city was devastated by a massive earthquake that killed 181 people. There were no initial reports of fatalities from the latest quakes.

The city's mayor, Bob Parker, said he had received unconfirmed reports of injuries within the central city cordon, where major building works have been under way since the quake of February 22, which destroyed much of the central business district and killed people. Workers had been evacuated from the "red zone" following the first aftershock, he said, avoiding further casualties.

The first of the aftershocks measured 5.5 magnitude and struck at 1pm New Zealand time, at a depth of 11km, 10km to the east of the city. The second, larger shake, was at 2.20pm, measured 6.0, and was centred 10km southeast of the city at a depth of 9km. A series of smaller shakes were also felt over a turbulent two-hour period.

Graduate student James Macbeth Dann was cycling on Barbados Street, the border of the "red zone" when the second of the two major quakes began. "At first I thought my tire had blown, and then I looked up and the street lights were rocking backwards and forwards," he said.

The gravity of the quake was immediately clear, he said. "The road was moving, the buildings were moving."

The shakes were felt as far afield as Dunedin in the south and Wellington at the foot of the North Island.

Building across the city were evacuated, including the city's airport. More than 50,000 homes lost electricity. The city's signature ChristChurch cathedral was reported to have suffered fresh damage.

The central-city Hotel Grand Chancellor, which slumped dramatically in the February quake, had tipped further towards the ground, said witnesses.

Fresh liquefaction emerged from the ground, with flooding reported in parts of the city's eastern suburbs. Residents described damage to homes, sewage leaks, and gridlock on the roads.

The prime minister, John Key, said: "It is another blow to Christchurch residents, who have already endured so much. However, today's events in no way weaken the government's long-term commitment to rebuilding Christchurch and surrounding areas."

He added: "The people of Christchurch should know that all New Zealanders are thinking of them and will continue to support and stand by them at this difficult time."

The region has been hit by dozens of earthquakes since a magnitude 7.1 shake in September last year, which caused widespread damage but no fatalities.