Lagos (Nigeria), Apr 24 (IANS): Boko Haram, a Nigerian rebel group which battled the military over the weekend and left 185 people dead, has become a major challenge for the security forces, pushing the army chief to ask soldiers to be alert and confront the guerrillas who use "unconventional weapons and tactics".

At least 185 people were confirmed dead in the weekend crossfire between the military and Boko Haram sect in Baga, a fishing community located in Nigeria's northeastern Borno State.

Army chief Lt.Gen. Azubuike Ihejirika described Boko Haram's activities as unconventional and asked army personnel to be at alert in order to confront the new trend in warfare that has been unleashed on the country.

Gen. Ihejirika's concerns came Tuesday, a day when the police in the northern state of Plateau said it had discovered a large cache of arms and home-made explosives which were to be used to blow up targets in Jos, the capital.

Some of these explosives have been used in suicide bombing in other parts of the country.

Plateau state's police commissioner Chris Olakpe said the arms were discovered during a search by the police, and expressed worry that large cache of arms have found their way into the hands of young people within the state.

As part of the efforts to face the Boko Haram threats, Gen. Ihejirika said the army is determined to reinforce the existing Quick Response Group.

It has also now been proved that most of the rebels use the country's porous borders to enter, make strikes, cause havoc and get out without being arrested.

Gen. Ihejirika admitted these rebels "employ all forms of unconventional weapons and tactics in urban and rural areas, capitalising on the porosity of our borders".

"From the creeks in the Niger delta to the Sahel savannah region in the northeast and northwest, there is no clear line between you and the adversary," he added.

Police sources in Maiduguri told IANS that the soldiers exchanged fire with the Boko Haram rebels at Baga which is on the Nigerian border with Chad.

Some locals have accused the soldiers of killing innocent civilians.

"They just entered the town to burn houses, forced people out of their homes and killed those who came in their way," said Idris Sanni, a trader.

Sanni said the community has buried 185 people. "This was just a slaughter and we did not know what these people had done to deserve this."

President Goodluck Jonathan has ordered an investigation into the killings.

Reuben Abati, special adviser to the president on media and publicity, in a statement said that President Jonathan "places the highest possible value on the lives of all citizens of the country and that his administration will continue to do everything possible to avoid the killing or injuring of innocent bystanders in security operations against terrorists and insurgents".

He said the investigation ordered by President Jonathan into the incident in Baga will determine whether or not the rules of engagement for the army were fully complied with.

Jonathan has ordered the National Emergency Management Authority (NEMA) and federal health agencies to work with the Borno state government in order to provide immediate relief and medical support for all who suffered losses and injury in the fighting at Baga.

Jonathan reminded the army to be alert to fight all forms of aggression against the country, both within and outside.

Based in Borno state, the sect had claimed responsibility for several attacks in which more than 1,500 people, including women and children, were killed since 2009 when it launched violent attacks in northern Nigeria.