The deaths take the number of British troops killed in Afghanistan to 171
Two British soldiers have been killed in an explosion in Helmand province, in southern Afghanistan.
A soldier of 1st Battalion Welsh Guards and one from 2nd Royal Tank Regiment were killed on Wednesday, the Ministry of Defence said.
UK troops last week launched a major offensive aimed at driving the Taliban out of strongholds in the province.
The deaths take the number of UK troops killed in Afghanistan since 2001 to 171. Next of kin have been informed.
A further six members of Nato forces were also wounded in the attack in Helmand, which involved an improvised explosive device (IED).
Spokesman for Task Force Helmand, Lt Col Nick Richardson, said there was a deep sense of loss as a result of the soldiers' deaths.
He said: "We grieve for them at this very sad time. Our thoughts and prayers are with their families, friends and colleagues who feel the greatest loss."
An MoD spokesman confirmed the soldiers had been killed while on Operation Panthers Claw near Lashkar Gah in central Helmand.
The operation is one of the UK military's biggest co-ordinated air operations of modern times.
It was launched to drive the Taliban out of strongholds in and around Babaji, north of Lashkar Gah.
The news of the two British soldiers' deaths came on the same day as the US army announced it had launched a major offensive against the Taliban, also in Helmand.
The US offensive involves nearly 4,000 US Marines and 650 Afghan troops.
The operation - named Khanjar, or Strike of the Sword - aims to clear insurgents from the region ahead of Afghanistan's presidential election in August.
Thousands of UK soldiers under Nato command have been fighting the Taliban in Helmand since 2006, but there has been criticism that they have been overstretched and under-resourced.