Boko Haram militants attacked troops from Niger on an island base in Lake Chad, the government said on Saturday, in a raid believed to have taken a heavy toll on the army. "At dawn on April 25, fighters from the terrorist group Boko Haram riding motorized canoes attacked the island of Karamga, a position northwest of the town of Bosso held by our defense and security forces," the ministry of defense said. "Operations are ongoing with the support of partners to counter the ambitions of this terrorist group," the ministry added in a statement broadcast on television.