KABUL (AFP) - Insecurity has handicapped preparations for Afghanistans key elections this week, with officials unable to confirm Monday the number of polling stations that will be open. Our main concern is security. We are coordinating with Afghan security agencies and doing our best to open as many polling centres as possible, electoral official Zekria Barakzai told reporters, three days before the vote. We will know the exact number of centres that will be open on election day, not before that, he added. On Sunday, Taliban insurgents threatened to attack polling stations, escalating their bid to derail Thursdays presidential and provincial council elections in the war-torn country. If they dont have soldiers and police we will not open the centres. Tribal elders (securing the buildings) are not an option for us, said Barakzai. Afghanistan is expected to mobilise all available security resources in a bid to protect voting centres on Thursday and overcome fears that poor voter turnout because of insecurity could jeopardise the polls legitimacy. About 200,000 Afghan security forces and the 100,000 US and NATO troops will provide security in a three-cordon formation, putting foreign forces on the periphery, followed by Afghan soldiers and then police at polling stations. Despite the influx of thousands of extra US troops and multiple offensives designed to crush rebel resistance, election officials have said insecurity could close up to 12 percent of the nearly 7,000 planned polling stations. The defence ministry said Monday that eight districts, all of them in southern Afghanistan where the Taliban are powerful, are outside government control and that 35 others faced a high-level insurgent threat. The districts which are under a high level of threat, where operations are ongoing even now, are 35, defence ministry spokesman general Mohammad Zahir Azimi told reporters in Kabul.