UK search and rescue teams assist in Christchurch

The mayor of Christchurch, Bob Parker, has praised the "incredible progress" made four days after a massive earthquake rocked the New Zealand city.

But rescuers admit the chance of finding survivors is now slim; no-one has been pulled from the ruins since Wednesday.

The death toll from Tuesday's 6.3 magnitude tremor stands at 144, with more than 200 still missing.

The BBC's Rachel Harvey reports from Christchurch where UK search and rescue teams are assisting with categorising the safety of damaged buildings.