(Updates with death toll) By Ghazwan Hassan TIKRIT, Iraq, March 21 (Reuters) - Scores of Gunmen took over a federal police headquarters in **rthern Iraq on Friday before ramming a tanker laden with explosives into the building, killing at least 15 people, a government official said. The mayor of the nearby town of Sulaiman Pek, 160 km (100 miles) **rth of Baghdad, said security forces later regained control over the village. Islamist militants occupied Sulaiman Pek last month and raised the black flag of the Sunni Islamic State in Iraq and the Levant (ISIL), a group inspired by al Qaeda, over it.