A team of 30 firefighters with sniffer dogs are flying out from RAF Lyneham in Wiltshire to Izmit, the centre of the devastation, the Department for International Development said.

They will be later joined by 10 men and another two sniffer dogs from the Gloucester-based charity Rapid UK, which specialises in search-and-rescue operations.

Around 40 Britons are already working in Turkey after they flew out on Tuesday night to join the international aid effort.

The BBC's Paul Welsh reports: "The first 48 hours are critical"

The mission left the UK as the government announced a £1.35m aid package for the earthquake victims.

International Development Minister George Foulkes said the government would respond to further requests for assistance as they came in.

'Unfolding tragedy'

Mr Foulkes said: "The scale of this tragedy is still unfolding, and we are unlikely to know the full cost in lives for many days.

This wrecked building in Izmit is viewed from a helicopter

"The immediate priority is to help with search and rescue.

"We are flying out a team of experts with specialist rescue equipment from fire brigades around the UK, as well as the International Rescue Corps, all skilled in search and rescue techniques."

The 40 specialists - including firefighters, paramedics, welders, mechanics and drivers - are taking with them thermal imaging cameras, videoprobes, special lighting and cutting tools.

Director of Rapid UK, Graham Payne: "The dogs will be instrumental in the rescue"

The volunteer rescuers include 27 firefighters from Cheshire, Leicestershire, Wales and the West Midlands. They are accompanied by 13 search and rescue specialists from the International Rescue Corps.

One of the firefighters, Shaune Farrell, of Leicestershire Fire Brigade, said: "We are ready and raring to go.

"I'm looking forward to getting out there and making a start. We rescue trapped people at home and I want to go there and help as many people as I can."

Mr Farrell, 40, said: "We are prepared to stay as long as we can - six to seven days is possible."

The team is under the command of a member of the Fire Service Inspectorate, Ted Pearn.

'Disaster veterans'

A spokesman for the team, Simon Webb, said: "They have a variety of skills between them and some of them have worked in Montserrat after the volcano, Macedonia on humanitarian relief, and after earthquakes in Kurdistan and Mexico."

Another team of 10 men and two sniffer dogs from the Gloucester-based charity Rapid UK is set to fly to Turkey on Wednesday.