Three aftershocks, one a strong 5.1 magnitude, rattled quake-weary residents of Christchurch late tonight.
Christchurch was ravaged by a 6.3 earthquake on February 22 which killed an estimated 182 people and has experienced many aftershocks in the month since then.
But three tremors rolled across the city in quick succession tonight, one of 3.0 at 9.43pm. the second of 5.1 four minutes later and the third of 2.9.
The second and third shocks were in almost exactly the same location - 10km east of the city, and 10km and llkm deep.
A Civil Defence spokeswoman told NZPA there were no reports of damage, but police and Civil Defence staff were checking building in central Christchurch.
Staff remained on standby at the Emergency Operations Centre at the Art Gallery.
One source told NZPA the first tremor was what Christchurch residents had become accustomed to as a "fairly standard" aftershock but the second jolt was much stronger and lasted a lot longer.
Many after shocks have been recorded since the "big one" of February 22.