The UK stands poised to help New Zealand after a devastating earthquake left at least 75 dead and caused widespread destruction, David Cameron has said.
A search and rescue team is to be deployed to Christchurch on the South Island, the Prime Minister added.
The pledge comes as emergency teams work through the night in the devastated city after reports that at least 300 people are trapped in ruined buildings.
Mr Cameron said: "The people of New Zealand have been hit by a devastating earthquake, not once, but twice in a matter of months, and I want to pay tribute to their resilience. They have our deepest sympathies and condolences.
"I have been in touch with my good friend, Prime Minister John Key, and he knows that Britain stands ready to provide whatever assistance is required in support of the local emergency services. We have agreed to send a search and rescue team, which has deployed immediately."
His comments came as the Queen spoke of her shock at the devastation caused by the quake.
"I have been utterly shocked by the news of another earthquake in Christchurch," she said. "Please convey my deep sympathy to the families and friends of those who have been killed; my thoughts are with all those who have been affected by this dreadful event."
Authorities say that 75 people died when the 6.3-magnitude quake struck around six miles (10km) outside Christchurch during lunchtime rush-hour. It is not known if any Britons are among the casualties.
Eyewitnesses said the three-mile (5km) deep tremor, believed to be an aftershock from a 7.1-magnitude earthquake which struck last September, levelled high-rise buildings, tore up pavements and sprayed rubble onto the streets below.
Mr Key warned that the death toll may rise, telling TV One News: "This may be New Zealand's darkest day."