Early wins in a major anti-Taliban push in southern Afghanistan offered a "beacon of hope," British Prime Minister Gordon Brown said Saturday during a surprise visit to troops.

During a lightning eight-hour visit to Helmand province, Brown cautioned that it was vital to "win the peace as well as the war" and vowed that British troops would stay in Afghanistan until their job was done.

"That's why it's so crucial that in just 20 days since the start of the operation, the combined international and Afghan forces, military and civilian, have begun turning a stronghold of brutal Taliban insurgency into a beacon of hope for local people," he told reporters.

Before Brown left Camp Bastion, one of the biggest military bases in Afghanistan, Britain's Ministry of Defence reported the death of a British soldier in an explosion in Helmand Friday.

The death in the Sangin district, which the ministry said was not connected to the ongoing assault that Brown referred to, brings to 269 the number of British troops killed since operations in Afghanistan began in October 2001.

In what is likely to be his last trip to Afghanistan before a general election expected on May 6, Brown met British troops at Camp Bastion and two frontline posts in Nad Ali, including one taken in Operation Mushtarak, currently under way in Helmand.

Mushtarak, in which US Marines have led 15,000 troops against Taliban insurgents in two poppy growing districts, Marjah and Nad Ali, is the first test of a counter-insurgency strategy for speeding an end to the war.

Around 4,000 of Britain's 10,000 troops in Afghanistan have been taking part in the campaign launched on February 13, in which troops are now consolidating control of the opium-producing target area.

Commanders on the ground have said they do not yet have complete control, but are paving the way for Afghan-led security and civil services.

Recent gains in Operation Mushtarak are set to be followed up in other Taliban strongholds in Helmand and neighbouring Kandahar province over the coming 12-18 months.

But the International Committee of the Red Cross (ICRC), in a strong statement issued in Kabul, warned that civilian control in the the Marjah area was still elusive due to the Taliban's lingering presence in the area.

The Marjah farming area had been so heavily mined with IEDs that civilians were largely confined indoors and the sick and injured could not be evacuated for help, the ICRC said.

"Improvised mines and other explosive devices are posing a deadly threat to civilians in Marjah," Reto Stocker, head of the ICRC in Kabul, was quoted in a statement as saying.

"They make it almost impossible for people to venture out or to evacuate the sick and wounded, who therefore receive little or no medical care," he said.

The Taliban is the only party in the Afghan war to use IEDs, said Bijan Farnoudi, the ICRC's spokesman in Kabul, adding: "The improvised mines in Marjah have been left behind in huge numbers by the Taliban."

Brown said training local police was a pivotal part of the plan to hand security over to the Afghans so foreign troops can start withdrawing.

"We will do everything we can to support you with the equipment necessary and the resources you need," Brown told an audience at the Helmand police training centre on the outskirts of Laskhar Gah, Helmand's capital.

Brown flew to Afghanistan after giving evidence to Britain's public inquiry into the Iraq war on Friday, when he denied accusations that he did not properly fund the military in that conflict when he was finance minister, before taking over as prime minister from Tony Blair in 2007.

"I've been planning this visit for some time," he told reporters in Helmand. "The last four years I have come here around this time just to meet the troops to see what progress has been made."