Taliban militants attacked a police base in northern Afghanistan, killing 11, possibly with help from at least one of the policemen inside, local government officials said Tuesday.\r\nThe insurgents first overran a checkpoint near the base late Monday, and were apparently able to breach the compound with ease because a sympathetic policeman opened a door for them.\r\nThese details were provided by Mabobullah Ghafari, a provincial councilman in Baghlan province where the attack took place. A local police official, speaking on condition of anonymity because he was not allowed to brief reporters about the attack, also gave the same account.\r\nInsider attacks have been steady throughout Afghanistan\u2019s 18-year conflict, with US and NATO troops most often targeted. But when Afghan security forces are targeted, the casualty rate is often much higher.\r\nLast July, two US service members were killed by an Afghan soldier in the southern Kandahar province. The shooter was wounded and arrested. In September, three US military personnel were wounded when a member of the Afghan Civil Order Police fired on a military convoy, also in Kandahar.\r\nNo group immediately claimed responsibility for Monday\u2019s attack on the outskirts of Puli Khumri, Baghlan\u2019s provincial capital. But the Taliban have a strong presence in the province and frequently target Afghan security forces in and around the city.\r\nLast September, the insurgents attacked Puli Khumri and blocked the city\u2019s main highway to the capital Kabul for more than a week.\r\nThe Taliban currently control or hold sway over around half the country.\r\nThe US and the Taliban are currently attempting to negotiate a reduction in hostilities or a cease-fire. That would allow a peace agreement to be signed that could bring home an estimated 13,000 American troops, and open the way to a broader post-war deal for Afghans.