The brother of a senior Afghan Taliban commander has been killed in a US missile strike in northwestern Pakistan, intelligence officials and a Taliban commander said Friday. The attack apparently targeted Siraj Haqqani, a senior figure in an Al-Qaeda-linked network. Four people were killed when missiles struck a house Thursday night in the Dande Darpa Khel of North Waziristan, two Pakistani intelligence officials said. One of the dead was Mohammed Haqqani, the brother of Siraj Haqqani, the officials said. It was not immediately known if Siraj Haqqani was at the house at the time, and if he was, whether he was hit by the blast, they said. A local commander of Pakistani Taliban in Mir Ali – a town in North Waziristan – confirmed to the AP that Mohammed Haqqani died in the missile attack with three of his associates Thursday. A relative from Haqqani's family told AP his funeral was held near Miran Shah, the main town in North Waziristan, and was attended by hundreds of residents and relatives. The strike at the heart of the Haqqani network comes close on the heels of a series of arrests – including the capture of the Taliban No. 2 leader – that together are being seen as the most significant blows in years to insurgents fighting US and international troops in Afghanistan. Jalaluddin Haqqani, believed to be in his 60s or older, is said to be too ill to do much now, and his son Siraj is running the network. The group is alleged to make its money through kidnappings, extortion and other crime in at least three eastern Afghan provinces. Also Friday, four Pakistanis working for the international aid group Mercy Corps were kidnapped by gunmen in the Qila Saifullah area of southwest Balochistan province, local police official Mohammad Iqbal said. Mercy Corps officials declined to offer any immediate comment. US Marines airdropped into Taliban territory Elite Marine recon teams were dropped behind Taliban lines by helicopter Friday as the US-led force escalated operations to break resistance in the besieged insurgent stronghold of Marjah. As the major NATO offensive entered its seventh day, about two dozen Marines were inserted before dawn into an area where skilled Taliban marksmen are known to operate, an officer said, speaking on condition of anonymity because of security concerns. Other squads of Marines and Afghans, marching south in a bid to link up with Marine outposts there and expand their territory, came under sniper fire and rocket attacks by midday. The rattle of machine-gun fire and the thud of mortars echoed nearby. “We had a few companies engaged in firefights that lasted a few hours,” said Marine spokesman Lt. Josh Diddams, who added that overall resistance appeared lighter than in previous days. The Marjah offensive is the biggest since the 2001 US-led invasion of Afghanistan and a test of President Barack Obama's strategy for reversing the rise of the Taliban while protecting civilians. A NATO statement said troops were still meeting “some resistance” from insurgents who engage them in firefights, but homemade bombs remain the key threat to allied and Afghan forces. Six coalition troops were killed Thursday, NATO said, making it the deadliest day since the offensive began. The death toll so far is 11 NATO troops and one Afghan soldier. Britain's Defense Ministry said two British soldiers were among those killed Thursday. No precise figures on Taliban deaths have been released, but senior Marine officers say intelligence reports suggest more than 120 have died. The officers spoke on condition of anonymity because they were not authorized to release the information. Hundreds of Afghan police began moving into a key Taliban stronghold Friday, in a first step towards expanding Afghan sovereignty over the south. The deployment of 400 specially-trained police, accompanied by about 80 US Marines, in the Marjah area of Helmand province was an indication that US-led troops expect to be in control of the area within days. “We're going to Marjah,” said police officer Sayed Safiullah, as the heavily armed convoy left the camp on the outskirts of Lashkar Gah, capital of the restive province. Officials said they would arrive in Marjah township Saturday to take over security in areas already cleared of Taliban fighters and booby traps. As US and Afghan troops moved south Friday, they continued to sweep through houses, searching for bombs and questioning residents. One man came forward to the Marines and revealed a Taliban position a mile (1.6 kilometers) away. The man, who was not identified for security reasons, said he was angry because insurgents had earlier taken over his home. He gave US forces detailed information, saying more than a dozen Taliban fighters were waiting to ambush troops there. The position was rigged with dozens of homemade bombs and booby-traps, he said. Other people interviewed said some Taliban fighters in the area were non-Afghan. “Some of them are from here. Some are from Pakistan. Some are from other countries, but they don't let us come close to them so I don't know where they are from,” said opium poppy farmer Mohammad Jan, 35, a father of four. Marines also uncovered a row of machine gun bunkers alongside a canal where they suspect enemy fighters had been firing on them the previous day. Located at a crossroads, the five newly abandoned bunkers, camouflaged under a layer of mud, aimed out across an open field. In the near distance, large stones had been set up to act as machine gun sights. “These guys aren't doing anything new, but it's pretty much the good basics of defense,” said Lt. Scott Holub, from Pasadena, Maryland. Outside of Marjah, US and Afghan troops, backed by Stryker infantry vehicles, pushed into a section of mud-walled compounds that had been occupied by the Taliban in the Badula Qulp region, northeast of town.