More than one in four of the British soldiers killed in Afghanistan since 2001 have been victims of roadside bombs, mines or booby-traps, The Herald can reveal.

More alarmingly, eight of the 18 killed in explosions fighting the Taliban in the past six years died since January, marking a major shift in insurgent tactics from the costly firefights and ambushes of 2006 and 2007 in which they were outgunned and defeated.

The Ministry of Defence admits the 27% fatalities in Helmand due to explosive devices is now just 1% less than the tally for UK bomb deaths in Iraq since 2003.

In Afghanistan, 68 soldiers have been killed in action or died of wounds, all but two of them since 2006, while 136 service personnel have been killed by insurgents in Iraq.

Military sources say improvised explosive devices (IEDs) designed to penetrate armour and believed to have originated in Iran have been used in recent Afghan attacks.

They also claim Taliban tactics are mimicking those of Iraqi resistance groups, and concentrating on striking remotely at vehicle patrols and convoys rather than risking fighters in open battle.

"The contrast between now and 2006 is stark," one veteran officer said yesterday. "They probably sustained between 5000 and 6000 casualties in less than two years. Now they're boxing a bit more clever, knowing they can't take us on and win in a straight firefight. It was predictable they would copy the Iraqis and go for the booby-trap option."

Meanwhile, Afghan security forces surrounded a house in the capital Kabul yesterday and traded fire with Taliban gunmen before blowing up the building and killing two militants. A woman and child inside also died, officials said.

The two dead Taliban fighters were involved in a botched attempt to assassinate President Hamid Karzai on Sunday but they also received help from some government officials, said Defence Minister Abdul Rahim Wardak.