A booby-trapped motorcycle exploded outside an Egyptian police training centre on Saturday, wounding 16 people, the interior ministry said.The apparent attack in the Nile Delta city of Tanta wounded 13 policemen and three civilian passersby, the ministry said in a statement.A militant group that calls itself Liwaa al-Thawra -- The Revolution Brigade -- claimed responsibility for the bombing in a statement posted on its social media accounts.Islamist militants have killed hundreds of policemen and soldiers, mostly in the Sinai Peninsula, since the military overthrow of Islamist president Mohamed Morsi in 2013.Militants have killed hundreds of policemen and soldiers, mostly in the Sinai Peninsula, since the military overthrow of Islamist president Mohamed Morsi in 2013.Most of the attacks have been claimed by the Islamic State group's Egypt franchise.