Three British soldiers have been killed by a roadside bomb in Afghanistan, Britain's Defense Ministry said on Wednesday, May 1, in the deadliest single attack on the British military there in more than a year, Reuters reported.

Nine Afghans were also killed in Tuesday's explosion that hit the soldiers' vehicle while it was on a routine patrol in Nahr-e Saraj district in the southern province of Helmand.

Another six British soldiers were wounded in the blast, which occurred two days after the Islamist Taliban movement launched its spring offensive, saying it would target foreign military bases and diplomatic areas.

"We have paid a very high price for the work we're doing in Afghanistan," Prime Minister David Cameron said in a morning interview on ITV television. "It is important work because it's vital that country doesn't again become a haven for terrorists, terrorists that can threaten us here in the UK."

The three British soldiers were the first to be killed by an attack while travelling in a Mastiff, an armored vehicle designed to withstand roadside bombs and sent to Afghanistan after a debate about whether previous equipment was adequate.

"Their deaths come as a great loss to all those serving in Task Force Helmand," said Major Richard Morgan, a spokesman for the task force. Their families have been informed.

A total of 444 British soldiers have been killed in Afghanistan since Britain's military involvement there began in October 2001, including six this year.

British troops are handing over security operations to Afghan forces and are due to end combat operations in Afghanistan by the end of next year.