KABUL (AFP) - Britain is "utterly resolute" in supporting Afghanistan as it fights a Taliban-led insurgency and pursues democracy, Prime Minister Gordon Brown said during a lightning visit to Kabul on Thursday. Brown flew into the Afghan capital from southern Helmand province where he met British troops at a sprawling base of the Nato-led International Security Assistance Force (Isaf), which is helping Afghanistan fight off the extremists. Even though countries with troops in Afghanistan had suffered losses in recent weeks, "we are utterly resolute in our determination to support this new democracy of Afghanistan," Brown said. Brown pledged more support for Afghanistan, especially in the training and mentoring of the army and police forces and development of the civil service. Britain would also provide $120m towards a development fund that would include paying teachers' salaries and $17m for a radio station in Helmand, he announced. Brown said he and Karzai - who described the prime minister as having a "kind heart" for Afghanistan - also discussed in their meeting allegations that attackers were arriving in Afghanistan from sanctuaries across the border in Pakistan. "I accept that Pakistan and the problems of terrorism there " that's something that's got to be raised with the Pakistan government," he said. Addressing about 300 soldiers during a 90-minute stopover in Camp Bastion in Helmand, he praised the "courage, professionalism and dedication" of the British forces in Afghanistan. He said their work would ensure a "terror-free Afghanistan but also an Afghanistan where there will be a democracy and people will have a stake in the future." Meanwhile, security gains made in southern Afghanistan could suffer if US Marines are pulled out later this year without replacements, the head of the Marine Corps has warned. General James Conway, the Marine Corps commandant, said the US Marines will be unable to provide more forces until there is a significant draw down of their numbers in Iraq. Meanwhile, Nato on Thursday denied that Alliance warplanes accidentally killed any of the 10 French troops who died in a Taliban ambush in Afghanistan. "As far as Nato and Isaf (Nato's International Security Assistance Force) are concerned, the allegations in Le Monde are completely unfounded," Alliance spokeswoman Carmen Romero said. "We deny the report... we have no information whatsoever that would indicate that the French soldiers were killed by NATO planes," Romero added.