For the second time in five months, New Zealand's south island city of Christchurch was rocked by a major earthquake on Tuesday afternoon local time.

Initial reports from Reuters news agency indicated that there were no reports of casualties, from the magnitude 6.3 temblor.

But the New Zealand Herald is reporting casualties and major damage to downtown buildings, including the Christchurch Cathedral.

In its live blog, the Herald reports phone lines down, water running through the streets, and several buildings with serious damage.

One blog entry says New Zealand's TV3 is reporting the Pyne Gould financial services building has collapsed. Another, unsubstantiated report claims that the cathedral has collapsed.The New Zealand Press Association reported that the TVNZ building in Christchurch had collapsed. And there's an entry that a facade of a building in downtown Christchurch has collapsed onto a bus, injuring passengers. NZTV is reporting at least one fatality.

Christchurch resident Jane Smith who works in the central city told the Herald a work colleague had just returned from helping rescue efforts after a building facade had collapsed on a bus on Colombo St.

"There's people dead. He was pulling them out of a bus."

"Columbo St is completely munted."

"We can't move at the moment because the city's gridlocked."

The quake occurred at 12:51 p.m., during a normal workday in Christchurch, according to the US Geological Survey. The epicenter was relatively shallow –just 3 miles deep – and close, about 6 miles from the country's second largest city, where some 26,000 full-time employees work.

"Obviously this earthquake has taken place at a time where people have been going about their daily business. We're doing everything we can to make sure that people are safe and are evacuating the central city," said New Zealand Prime Minister John Key, about an hour after the quake hit. After an emergency cabinet meeting scheduled for 3 p.m. local time, the prime minister is scheduled to fly to Christchurch.

The city was struck by a force 7.1 quake last September, Reuters reports, which caused serious damage and dented the national economy but caused only minor injuries.

"The quake is significantly smaller than the previous Christchurch earthquake, however it was very shallow and might have been very close to the centre of the city," Civil Defence spokesman Vince Cholewa told the Herald

"We are still getting a picture of what has happened..."