The British Army plans to keep a garrison in Iraq until at least 2012, according to a leaked document detailing future deployments.

The disclosure comes as an opinion poll reveals that two-thirds of Scots want an immediate withdrawal of all troops from Basra and the US military announced the deaths of six US soldiers yesterday.

Three were killed by a roadside bomb during a patrol south of Baghdad. Another died in a separate mortar or rocket attack south of the capital. Two more soldiers died of wounds sustained in combat in Diyala and Salahuddin provinces, north of Baghdad.

The poll, for BBC Scotland, shows 66% of those questioned want a prompt pull-out, while 31% are opposed.

It follows a week in which six British soldiers died in ambushes in the south, including four killed when their vehicle was destroyed by a bomb near Basra on Thursday.

The death toll was the worst in a week from enemy action since the 2003 invasion and brought the total of UK fatalities to 140, 109 of whom died at the hands of insurgents.

At least 15 Iraqi civilians also died yesterday when a truck bomb exploded near a hospital in Mahmudiya, south of Baghdad.

The British military tour plot lists units earmarked for operations on a rolling cycle, which gives soldiers and their families an indication of leave and training time between stints of frontline service.

The document shows 12 Mechanised Brigade, which has completed an Iraq tour and is due to be sent to Afghanistan, has been told it will be back in Basra in five years.

Units serving in Iraq refer to their six-month tours under the codename Telic. The current garrison is on Telic 9. The plot plans ahead for Telic 19.

Almost 100,000 of the 180,000 men and women in the UK's armed services have been deployed to southern Iraq. Several units, such as the Black Watch, have served more than one tour.

Meanwhile, thousands of Iraqis streamed to the holy city of Najaf yesterday after fiery Shi'ite cleric Moqtada al Sadr called for a big anti-American protest today. Sadr, who blames the US-led occupation for Iraq's unrelenting violence, urged a protest on the fourth anniversary of US forces entering Baghdad.