At least four suicide bombers were killed and two policemen injured as militants attacked a police station in Pakistan's northwest Bannu district early Thursday morning, local media reported. Urdu TV channel Geo reported that the attack was launced at about 5:30 a.m. (local time) when at least seven heavily armed suicide bombers attacked Miriyan police station in Bannu, a main district of the country's northwest Khyber Pakhtunkhwa province, from two directions. The militants wanted to incur a huge loss to the police by entering inside the police station but the alert cops retreated their attack by forceful retaliatory action, said the report. Four suicide bombers were shot dead during the counter-attack while three others are still engaged in cross-firing with the police. The attack was followed by a fierce exchange of firing between both sides. Heavy contingent of police and army reached the spot and cordoned off the area. Some media reports said that exchanges of firing between militants and security forces are still continuing, while some reports quoted eyewitnesses as saying that the militants fled to some unknown direction and security forces are carrying out a search operation in the nearby area. No group has claimed responsibility for the attack yet. This was the second attack on police since this morning. In an earlier attack, militants hurled five hand grenades at a police station in neighboring Karak district, but no causality was reported.