Nigerian militants 'under siege'
A group of Nigerian Islamist militants is barricaded inside a district in the city of Maiduguri, after two days of violence in the country's north.
A BBC reporter in the city says the Islamists, known locally as the "Taliban", are shooting at anyone approaching their stronghold.
The military says it has killed three militants trying to join the group.
The security forces have been told to use all necessary means to end the unrest, which has killed at least 100.
Sporadic fighting has been reported throughout the day in Maiduguri, with gunshots being heard and plumes of smoke rising from buildings.
"Fighting is still raging on in the heart of the city, where these men are burning places," a police officer told the AFP news agency.
Witnesses said dozens of corpses - mostly of militants - were still strewn around the city's police headquarters, which was the target of Monday's attacks.
The militants are occupying an area near Maiduguri's railway station which includes shops, schools and the home of their leader Mohammed Yusuf.
Also in the area are the mosque where he preaches and the headquarters of his group, known as Boko Haram, which translates as "Western education is prohibited".
Mr Yusuf says young people in the region are being corrupted by the West.
Although the group is also known locally as the "Taliban", they are not thought to have any links to the Afghan group.
It is not known how many people are inside the barricaded area.
The BBC's Caroline Duffield in Nigeria says armoured vehicles and soldiers are pouring into the city.
She says the militants are shooting indiscriminately at civilians and hundreds are fleeing the district.
Bodies piled up
The military has stepped up security in the north of the country following the clashes.
Soldiers set up road blocks and imposed dusk-to-dawn curfews in the worst affected areas of Yobe, Kano and Borno States.
Earlier the military said it had killed three members of Boko Haram, who they said were coming from Kano State to join the group in Maiduguri.
One of those killed is believed to be a senior member of Boko Haram in Kano.
In two days of violence, the militants staged attacks on police and government offices.
There have been reports of youths armed with machetes and guns killing police officers and civilians at random.
Eyewitnesses told the BBC that police stations were attacked and civilians pulled from their cars and shot dead.
Maiduguri, in Borno State, has seen the worst violence. The bodies of residents and militants have been piled outside the police station and in the streets.
A BBC reporter said there were about 100 corpses on Monday, and other witnesses said at least 30 bodies remained there on Tuesday.
Maiduguri police said 103 had died in the violence in the city, including 90 members of the Boko Haram, eight police officers, three prison officials and two soldiers.
Sharia law is in place across northern Nigeria, but there is no history of al-Qaeda-linked violence in the country.
The country's 150 million people are split almost equally between Muslims in the north and Christians in the south.