Hundreds of people have died in detention facilities in north-east Nigeria as the army tries to crush an Islamist militant rebellion there, according to Amnesty International. The human rights group said some detainees died from suffocation in overcrowded cells, others from starvation and extra-judicial killings. In the report, it calls for an urgent investigation into the deaths. Nigeria's Interior Minister Abba Moro has dismissed the report as "not true". "I want to assure you - this government will not take the lives of any of its citizens... including those who have taken up arms against the government," he told the BBC's Focus on Africa programme. A senior Nigerian army officer told Amnesty that at least 950 people had died in military custody during the first half of this year. Most had been accused of having links to the Islamist militant group Boko Haram, Amnesty said. Boko Haram is fighting to overthrow Nigeria's government to create an Islamic state, and has launched a number of attacks on schools. About 50 students were shot dead earlier this month in their hostel, in an attack blamed on Boko Haram. A state of emergency was declared in three northern states in May - Yobe, Borno and Adamawa - in response to thousands of deaths in militant attacks.