A series of earthquakes measuring 5.8 magnitude has hit the New Zealand city of Christchurch.

No tsunami warnings were issued but the authorities evacuated public buildings and Christchurch international airport as a precaution.

Warwick Isaacs, demolitions manager for the Canterbury Earthquake Recovery Authority, said most buildings had been evacuated as an emergency measure. Casualty figures are unknown but a num ber of people have been treated for injuries.