LAGOS, May 10 (Reuters) - Al Qaeda Islamist militants have renewed their threat to bomb targets in Nigeria, Africa's top oil producer, a newspaper reported on Saturday quoting the national police chief. The United States embassy in Nigeria said last September the country was at risk of "terrorist attack" and Osama bin Laden once named the world's eighth biggest oil exporter as ripe for jihad or Islamic holy war.

"The al Qaeda network has threatened to send time bombs to Nigeria ... CPs (commissioners of police) of all the commands should be on the alert and ensure that these items (bombs) do not pass through their end," the Punch newspaper quoted Inspector General of Police Mike Okiro as saying.

He gave no details of what the targets might be, but he told a group of senior officers on Friday that intelligence reports showed the threat was real.

A number of suspected jihadists have been arrested by police and the State Security Services (SSS) in recent years, but the cases have dragged on in the courts and there have been no convictions. No conclusive evidence of al Qaeda's presence in Nigeria has been made public.

Five Islamist militants with suspected links to al Qaeda are on trial in the capital Abuja for plotting attacks on government targets in Africa's most populous country.

The men were arrested in November by the SSS in mainly Muslim northern Nigeria. Three of them have also been charged with training in Algeria with the Salafist Group for Preaching and Combat (GSPC) between 2005 and August 2007.

The GSPC renamed itself al Qaeda in the Islamic Maghreb in January 2007.

The charge sheet said the five militants, all in their early 30s, "did conspire to commit terrorist acts," and said three of them trained in Algeria "with intent to attack government facilities and cause insurrection in Nigeria".

Another charge said the militants had an AK 47 rifle, ammunition, dynamite, fertiliser "and 11 explosive devices" which they planned to use to attack government facilities and installations in the southern cities of Lagos and Ibadan.

Nigeria's 140 million population is roughly equally split between Christians and Muslims. The two groups usually live side by side peacefully, but there are occasional outbreaks of sectarian conflicts.

Tensions heightened in 2000 after 12 mainly Islamic northern states began a stricter enforcement of sharia, alienating sizeable Christian minorities. Thousands were killed in sporadic riots across the country.

(For full Reuters Africa coverage and to have your say on the top issues, visit: http://africa.reuters.com/) (Writing by Tume Ahemba; Editing by Matthew Jones)

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