Update (6:04 p.m.): Secretary of State Hillary Clinton has decried the "cowardly attack" saying "We will take all necessary steps, not only to ensure the safety of our people, but to secure the area and to ensure that those who perpetrated this attack are dealt with." In total, at least 9 people were killed and 23 injured in the fighting, Reuters reports.
Update (12:08 p.m.): Kabul's police chief tells NBC News that four Afghan police and two civilians were killed in the attack and security forces continue to fight to take control of the over-taken building.
Update: NBC News reports that the insurgents waging the attack are Taliban suicide fighters. Two have been killed and two more continue to fight. In a statement, the Taliban said "several attackers armed with rocket-propelled grenades and suicide vests were targeting government buildings near the city's embassy district." Taliban spokesman Zabihullah Mujahid told NBC News, "With the help of our sincere mujahideen with Afghan army, police and government, our fighters managed to enter this high-security zone and carry out such attacks." According to reports, the insurgents took over a high rise building near the U.S. Embassy and began firing rocket-propelled grenades from that location.