Two suicide bombers wearing police uniforms have blown themselves up at an Afghan police headquarters in the east of the country, killing at least 12 officers and wounding another 16.Nawab Waziry, the head of Paktika's provincial council, said the bombers passed through three security gates unhindered before reaching the main building of the police compound. One detonated the explosives he was wearing inside the building, while the other blew himself up near its entrance, he said."The site was covered with blood," Waziry told The Associated Press news agency.The Taliban claimed responsibility for the attacks in a message emailed to the media. Paktika is one of the most violent areas in Afghanistan. It is south of Kabul and borders the Pakistani region of North Waziristan - long a refuge for the Taliban and allied groups. Nato and Afghan forces face daily violence against the Haqqani group, a Pakistan-based ally of the Taliban, which operates in the area. In a separate incident, Nato-led forces came under attack near a compound in the district of Sherzad in Nangarhar province. Nato responded with air raids and the attackers were killed in the battle that ensued. There were no casualties on the Nato side.