The Nigerian government has banned a radical Yoruba organisation which is responsible for the murders of hundreds in Lagos in days of fighting between the country's two largest ethnic groups.
President Olusegun Obasanjo proscribed the widely supported Odua People's Congress (OPC) and ordered the arrest of its leadership and members amid another surge in the ethnic violence that many Nigerians fear is a further step toward the Balkanisation of their country.
Nigeria's senate empowered Mr Obasanjo to declare a state of emergency in Lagos, in the south-west of Nigeria.
Thousands of Hausa families originally from northern Nigeria have sought protection in military barracks as soldiers have been deployed in the centre and suburbs of Lagos to stop the killings by Yoruba militants. Bodies were still lying in the street yesterday amid torched cars and buses and razed buildings.
"Such brutal and irresponsible acts cannot and must not be tolerated in a civilized society," Mr Obasanjo said.
"Therefore, law enforcement agencies are hereby ordered to arrest and prosecute any person who claims or presents himself as a member of the OPC and similar organisations, all of which are hereby declared illegal, unacceptable and a serious threat to the peace and security of Nigeria."
The police say they have picked up more than 200 people, including two OPC leaders. "We are going for the OPC leaders one by one. We have a list of its leaders," the Lagos police chief, Mike Okiro, said.
The Red Cross said at least 100 people have been killed - although this figure is probably an underestimate - and 20,000 have been forced from their homes by the violence which began on Sunday as Yoruba militants pursued alleged thieves into a mainly Hausa area of Lagos. The attacks spread to many other parts of the city, including parts of the business district.
Until now, Mr Obasanjo has trodden carefully around the OPC but the latest bloodletting is expected to lead to retaliatory attacks against Yorubas living in northern cities.
It has also raised the spectre of the first attempt at secession by a Nigerian region since Biafra's failed bid for in dependence three decades ago in which more than a million died.
The OPC was founded six years ago to promote the interests of 20m Yorubas living in Nigeria's south-west, where there is widespread resentment at years of military rule under the northern-dominated army.
Popular support for the organisation surged after it emerged from the underground with the return of civilian government last year - just as northern states rushed to introduce hardline Islamic law, including amputations for theft and lashes for adultery.
The imposition of Sharia law is widely viewed as a form of ethnic persecution by the mostly Christian southerners living in northern Nigeria. It has increased public backing in Lagos for the OPC's demand for political autonomy or even outright independence for south-western Nigeria.
The ban on the OPC came after the leader of its moderate wing, Dr Frederick Fasehun, refused to sign a joint communique with Hausa leaders calling for an end to the violence. It is not clear if he is among those arrested.
The police have spent nearly a year hunting the leader of the organisation's more radical faction, a cabinet maker called Gani Adams, who has become a folk hero in Lagos.
He has eluded capture despite a price put on his head by the authorities and radical northern organisations for leading the ethnic killings of thousands of Hausas and eastern Igbos in Lagos. The murders provoked retaliatory massacres in other parts of Nigeria.
Underpinning the rise in Yoruba nationalism are fears that growing disillusionment with Mr Obasanjo's government could lead to a return of military rule. His failure to revive Nigeria's economy and his bitter battles with the country's corruption-plagued parliament have been compounded by accusations of ethnic favouritism on all sides.
Mr Obasanjo, a Yoruba, has lost support in south where he is charged with being soft on the militant Muslims behind the constitutionally questionable enforcement of Sharia law. In the north, he is accused of ignoring OPC excesses.
The information minister, Jerry Gana, rejected the latter charge by reminding Nigerians of the near-total destruction of the south-eastern town of Odi by the army when it was ordered to quell unrest there.