Nigerian President Goodluck Jonathan said Sunday that his government was not currently in talks with Boko Haram Islamists, adding it was impossible to negotiate with a group that has "no face."
Jonathan has indicated a willingness to enter into dialogue with the insurgent group, which is blamed for hundreds of deaths in the country since 2009.
In August, his spokesman Reuben Abati confirmed for the first time that officials had opened back-channel talks with some members of the group.
But on Sunday, in a national broadcast in which he took questions from a panel of journalists, Jonathan said: "There is no dialogue with Boko Haram and government...there is no dialogue that is going on anywhere.
"There is no face so you don't have anybody to discuss with," he added.
Boko Haram is believed to be made up of several different cells and it is not clear that the group has leaders who can credibly negotiate on its behalf.
What is believed to be the main branch of Boko Haram, led by Abubakar Shekau, has repeatedly ruled out dialogue.
Shekau, designated a global terrorist by the US, has remained mostly hidden from the public, apart from a series of videos posted on YouTube in which he is pictured with a Kalashnikov rifle while making a variety of threats.
In a media interview after Boko Haram's deadliest ever attack in January, Jonathan urged the group to state its grievances.
The Islamists have consistently called for the creation of an Islamic state in Nigeria's mostly Muslim north, but their other demands have repeatedly shifted.
Their insurgency is estimated to have left 2,800 people dead, including killings by the security services.© ANP/AFP