British casualties in Afghanistan have reached almost the same levels of deaths and injuries as those suffered by the garrison in Iraq over the past 18 months, according to Ministry of Defence figures.

The death in action of a Royal Marine in Helmand yesterday brought the toll in Afghanistan to 63 since the start of 2006, just three short of the number killed in Iraq over the same period.

The tally of those wounded in action in that timescale is now 203 in Afghanistan compared with 236 in Iraq, including 26 and 31 respectively with life-threatening injuries.

July has been one of the worst months for British casualties, with four servicemen killed by Taliban insurgents in the past five days in Helmand and six dead from mortar and rocket fire in Basra.

The latest fatality happened during operations in Helmand on Sunday.

An MoD spokeswoman said the Royal Marine's next-of-kin had been informed, but had asked for 24 hours' privacy before his name is released.

The UK has 7100 troops in Helmand compared with 5500 in southern Iraq. Up to 1500 of the former have been involved in a week-long joint mission with 500 Estonian, Danish and US soldiers designed to penetrate Taliban territory.

Operation Chakush, or Hammer, is part of a wider plan to clear insurgents from the areas surrounding the Kajaki Dam, a project which will provide electricity for most of southern Helmand and improve the lives of more than 1.5 million farmers and civilians if and when it is completed.

Efforts to harness the power of the Helmand River and its tributaries have been hindered deliberately by the Taliban, who fear that positive improvements to infrastructure will deprive them of support in their own heartland.

Some of the fiercest fighting in Helmand since 2001 has taken place near the dam as successive UK battlegroups pushed back Taliban outposts, only to have the insurgents return when they withdrew from captured compounds and villages.

Overall British military deaths from all causes in Afghanistan stand at 68 since the first, limited allied intervention in 2001. A total of 63 have died since the start of 2006, of whom 45 have been killed in action.

The comparable death toll in Iraq since 2003 is 163, with 124 classed as killed in action or died of wounds.