The lethality of Nigeria's Boko Haram sect is escalating sharply into a serious security threat in the strategic West African giant, the continent's most populous nation and a major oil exporter.

The militants, whose name in the Hausa language means "Western education is sinful," have carried out a string of bombings in recent weeks that have killed around 150 people.

All told, around 250 people have died in Boko Haram attacks, including suicide attacks, this year as the group has extended its increasingly deadly strikes into urban areas outside their northern strongholds.

This has heightened concerns the group is being coached by jihadist militants in North Africa, al-Qaida in the Islamic Maghreb, and al-Shabaab in Somalia.

If there is a link-up between the Nigerian militants and al-Qaida branches it marks a dramatic expansion of jihadist-inspired terrorism in Africa, coming to Nigeria as it does from both the north and the east.

There's no concrete evidence to confirm the concerns. But several government officials and diplomats in Abuja, speaking off the record, have said it's the only rational explanation for the dramatic escalation in Boko Haram violence in recent months.

In June, AQIM leader Abu Musab Abdel Wadoud declared his group would provide Boko Haram with support and weapons to build strategic depth for the jihadists in Africa, now emerging as a major source of oil.

Nigeria is the fifth largest supplier of crude oil to the United States.

Wadoud may have been making empty threats. But the U.S. global security consultancy Stratfor noted it has "received reports that Nigerians associated with Boko Haram had been seen at AQIM training camps" in the Sahel region of North Africa.

"Some even had received training from al-Shaaab in Somalia."

The indications are that Boko Haram has split into up to three factions, two of them prepared to negotiate with the problem-plagued federal government of President Goodluck Jonathan, a southern Christian.

The third, determined to impose Islamic religious Shariah law, plans to pursue violent action.

It is believed to be led by a militant named Abubakr Shekau, who was once the deputy of Boko Haram leader Mohammed Yusuf, who was killed by the security forces in 2009.

Nigerian authorities thought they had crushed Boko Haram after killing Yusuf. They paraded his body on national television following bloody clashes with Christians in which some 700 people were slain.

Nigeria's population of 150 million is roughly split evenly between Muslims in the north and Christians in the south.

At that juncture, the Islamist campaign was rudimentary, using weapons such as machetes, clubs and some small arms in the sectarian battles in the north.

Then the Islamists took to motorcycles to carry out a wave of assassinations against security personnel to avenge Yusuf.

And finally, a year ago they began conducting car bomb attacks, initially against Christians in the flash point town of Jos in northeastern Borno state, then moving south for the first time.

Until then, Boko Haram's depredations attracted relatively little international attention. But that changed dramatically when they began launching high-profile suicide attacks against Nigeria's administrative capital, Abuja.

Suicide bombings are a tactic hitherto unknown in Nigeria but which are regularly employed by AQIM and al-Shabaab.

On June 16, Bako Haram made what Stratfor analyst Scott Stewart terms "a huge operational leap" with its first suicide car bombing against the federal police headquarters in Abuja.

It was their boldest and most complex operation to date, blasting their way into the country's political core in a direct challenge to Johnson's presidency. At least two people were killed. Nigeria's police chief narrowly escaped.

Stewart noted that "while that attack proved largely ineffective … it nonetheless represented a significant tactical development in that it demonstrated that Boko Haram had mastered a completely new aspect of terrorist tradecraft."

On Aug. 26, Boko Haram struck again in Abuja with a more refined and bloodier attack. They blew up the U.N. compound in the capital's diplomatic quarter, the group's first international target. Twenty-four people were killed.

On Nov. 4, a suicide bomber hit a military base in Maiduguri, Boko Haram's spiritual home in Borno, while conducting a conventional bomb blitz in other parts of the city. The Nigerian Red Cross reported more than 100 dead.