Three British paratroopers were killed in the southern Afghan province of Helmand on Sunday in a suicide bomb attack, bringing total British military deaths in Afghanistan since 2001 to 100.

The Ministry of Defence said the three soldiers from the Parachute Regiment had been on a routine foot patrol close to their Forward Operating Base in the Upper Sangin Valley when their patrol was attacked.

"Four soldiers were injured in the attack and were evacuated to the medical facility at Camp Bastion," the Ministry of Defence said in a statement.

"Sadly one soldier was pronounced dead on arrival and despite the best efforts of the medical team, two of the soldiers died as a result of their wounds.

"A fourth soldier is currently receiving treatment for his wounds and is expected to make a good recovery."

Chief of the Defence Staff, Air Chief Marshal Sir Jock Stirrup, said he regretted the deaths but vowed they would not be in vain.

"Right across the country, the international effort is beginning to affect real change. Ordinary Afghans face immense hardships but bit by bit life is improving. In parts of Afghanistan which were once lawless, there is now governance and rule of law.

"...Taliban influence is waning, and through British blood, determination and grit, a window of opportunity has been opened."