A magnitude 6 earthquake that struck Christchurch around 2.20pm was "very, very scary", Mayor Bob Parker said.
Buildings have collapsed and there have been reports of injuries following a series of quakes early this afternoon before the magnitude 6 one struck in a city that is trying to recover fromdamage inflicted by major quakes in September and February.
"Thank God, we had evacuated the whole of red zone, there's been quite clearly a more significant building collapse in there," Mr Parker told Radio New Zealand.
"We are just now being enveloped by dust blowing out of the central city, we are just outside the cordon.
"This time a plethora of sirens have gone off.... car signs, building sirens, it's just terrible.
"I am very, very concerned about our teams that have gone in there to check that people are out."
Mr Parker described the magnitude 6 quake as frightening.
"We don't know where that one has come from yet, but that was very, very scary."
Apartments next to the Art Gallery building had swayed. "I have never seen swaying like that," he said.
"My view anecdotally is that that was stronger than we first one we got this afternoon," he said referring to a 5.5 shake.
He said he was focusing on pulling together an overall picture and directing essential services to where they were most needed.
