Further troops will be withdrawn from Afghanistan, David Cameron will announce today, having paid tribute to the latest British soldier to have died there.

About 20 seconds into John Ware's film Afghanistan: War without End? there was a heart-lifting shot of a Chinook landing in an Afghan compound, bright purple smoke swirling into the vortex created by its blades. It was a strangely lovely thing to look at – if you could detach it from its context – but unfortunately it was the only thing to make you smile in an hour-long account of the gap between Western fantasies and Afghan reality. Not a good choice as an anti-depressant, obviously, a documentary about Afghanistan over the past 10 years. But even after you'd made allowance for that the film still managed to lower the spirits.

Straying beyond the normal boundaries of diplomatic nicety, the American Ambassador to Afghanistan, Karl Eikenberry, delivered a sharp verbal slap to President Hamid Karzai yesterday for his criticism of Nato's operations in his country implying that the US was becoming weary of it.

In 2004 the newly inaugurated President, Hamid Karzai, called for a jihad against Afghanistan's multibillion-dollar drugs industry, a rallying call for a campaign that would cost British taxpayers alone £850m between 2002 and 2009. Yet last year a UN report claimed Afghanistan's drugs underworld "is connected through payment and patronage to senior political figures who provide the required protection".

In a morning of close quarters combat in the heart of Taliban country, a Royal Marine team found themselves trapped in an ambush. Their section commander, a corporal, fell shot to the ground. Sam Alexander grabbed a heavy machine-gun and traded fire with insurgents just 15 metres away while charging forward. Running out of ammunition, he fired with his 9mm pistol until that too was spent. But he had done enough: the enemy fled.

Twelve people were killed and 80 injured in violent protests yesterday against the killing of two men and two women in a night-time raid by foreign troops in northern Afghanistan.

A suicide bomber crashed a car into a police bus, killing 14 people and wounding 16, said Zemeri Bashary, a spokesman for the Interior Ministry. Most of the casualties were police officers, he said.

The Pakistan Government denied media reports yesterday that it was lobbying Afghanistan to drop its alliance with Washington and look to Islamabad and Beijing to forge a peace deal with the Taliban and rebuild its economy.

A former cabinet minister has been arrested on corruption charges and a senior adviser to the President, who is also a former central bank chairman, has been questioned amid a growing banking scandal.

Not content with launching an English-language magazine that debuted with a feature called "How to make a bomb in the kitchen of your Mom", al Qa'ida's media wing has followed up with a magazine for women, mixing beauty tips with lessons in jihad.

Nato troops shot dead an aged relative of Afghan President Hamid Karzai after mistaking him for an insurgent, Afghan officials said yesterday, as anger continues to grow over civilian casualties. Haji Yar Mohammad, a second cousin of the President, was killed during a Nato night raid in the village of Karz in southern Afghanistan.