Taleban killed six UN foreign staff in an attack on an international guest house in Kabul Wednesday, deepening concerns about security for a presidential election run-off due in 10 days. The resurgent Taleban have vowed to disrupt the Nov. 7 run-off as US President Barack Obama weighs whether to send more troops to Afghanistan to fight an insurgency that has reached its fiercest level in eight years. In another sign of the growing reach of militants, rockets were also fired at a foreign-owned luxury hotel near the presidential palace in the heart of the Afghan capital, forcing more than 100 guests into a bunker, a hotel guest said. The Taleban said they had targeted the guest house because of the United Nations's role in helping organize the run-off vote. “We have said that we would attack anyone engaged in the process and today's attack is just a start,” Taleban spokesman Zabihullah Mujahid told Reuters by telephone. The US embassy said one American was among those killed. The UN said the attack would not deter it from its work, adding however that it may review security measures. The nationalities of the UN staff killed in the Kabul guest house attack were unclear. The sound of gunfire and sirens echoed across the capital for hours. Adrian Edwards, a UN spokesman in Kabul, said six UN staff had been killed and nine wounded. The attackers wore police uniforms to secure entry into the guest house, police said.