GARMSIR, Afghanistan, (AFP) - Two British soldiers and two police were killed in southern Afghanistan where thousands of troops have moved into Taliban strongholds ahead of August polls, officials said Sunday. Afghan, US, British and Danish security forces are pushing into parts of Helmand, an opium-producing province where the Taliban have established a firm grip, in some of the largest operations since the Talibans 2001 ouster. The forces have met with little resistance, although some 200 Marines have seen days of heavy fighting, commanders said, adding that many areas have been seeded with mines, a commonly used Taliban guerrilla tactic. The 200 US Marines fighting to hold the position arrived at dawn on Thursday, and they were still engaged in fierce combat through the weekend, Maj Dan Gaskell told AFP at nearby Camp Delhi. Two British soldiers were killed near the town of Gereshk in the centre of the province on Saturday, one in a rocket-propelled grenade attack and the other in an explosion, the Ministry of Defence in London said in a statement. However, the multinational Nato-led force in which the British military is a significant partner said that both were killed by an improvised explosive device (IED). The soldiers were involved in Operation Panthers Claw, a British-led campaign launched on June 23 to secure an area between Lashkar Gah, the capital of Helmand, and Gereshk further north. The operation kicked off with 350 troops in its first phase but now involves 3,000 British soldiers along with around 400 Danes and more than 300 Afghan soldiers, spokesman Lieutenant Colonel Nick Richardson told AFP. The latest stage started Friday, when more than 750 British and Afghan troops began sweeping through the area in vehicles and on foot, uncovering more than 50 IEDs in one area, a statement from the British military said. Around 4,000 US Marines, newly deployed to Afghanistan, are meanwhile on the fourth day of a major operation south of Lashkar Gah were they had teamed up with nearly 600 Afghan forces. Troops from Echo company of the 2/8 infantry battalion flew in by helicopter to Mian Poshteh, a key canal and road junction in Helmand province, as part of President Barack Obamas efforts to finally defeat the militants. The 200 Marines fighting to hold the position arrived at dawn on Thursday, and they were still engaged in fierce combat through the weekend, Maj Dan Gaskell told AFP at nearby Camp Delhi. They had encountered little resistance except for a pocket at Mian Poshteh, a key canal and road junction in Garmsir district, where a Marine was killed by hostile fire on Thursday. They have been fighting to hold that position, Maj Dan Gaskell told AFP at nearby Camp Delhi. He said about 40 Taliban fighters were using small arms, rocket-propelled grenades and rockets against the Marines, who have based themselves in a walled compound. Two of the Afghan policemen involved in the Helmand operations were killed in a mine explosion on Saturday, Interior Ministry spokesman Zemarai Bashary told reporters, without being able to give details. Significant resistance is not being seen, he said. Joint security forces are quickly moving ahead.