Kano - Boko Haram's abduction of more than 100 schoolgirls in Dapchi, northeastern Nigeria, shows the Islamist group still has the ability and means to stage major attacks.Since the raid last Monday, questions have been asked about how heavily armed fighters were able to storm the town in Yobe state without encountering any resistance, then disappear.Nigeria's military claims to have the region locked down, as part of a counter-insurgency effort against the group whose nearly nine-year campaign of terror has killed at least 20,000 people.But witnesses in Dapchi and analysts told AFP that it was a "well-planned attack" that specifically targeted the state-run boarding school.Residents in the dusty town near the border with Niger described seeing a convoy of at least 10 to 15 vehicles just as most people were at the mosque for evening prayers.Civilians were not harmed and the armed men instead asked for directions to the girls school. Hundreds of students at the Government Girls Science and Technology College fled in the dark into the surrounding bush; 110 have yet to return.Tip off? The attack and the confusion that followed recalled the abduction of 276 girls from Chibok, in neighbouring Borno state, in April 2014.That brought Boko Haram - whose name translates from Hausa as "Western education is forbidden" - worldwide notoriety at a time when it controlled swathes of territory.Since early 2015, that strength has disappeared.KEEP UPDATED on the latest news from around the continent by subscribing to our FREE newsletter, Hello Africa.FOLLOW News24 Africa on Twitter and Facebook. But Yan St-Pierre, a counter-terrorism specialist with the Modern Security Consulting group, said: "If they kidnapped more than 100 girls, that shows they have sizeable means at their disposal and a secure place to take them."Another worrying indication, according to the Yobe state governor Ibrahim Gaidam, is that soldiers stationed at strategic checkpoints in Dapchi, were redeployed last month.That left ordinary uniformed police as the town's only defence. One resident, Mohammed Adam, 27, said they were not effective: "They ran into the bush."Another Dapchi resident, who asked not to be identified, said he was concerned that Boko Haram sympathisers had secretly infiltrated the town."I believe informants tipped them off that the troops had withdrawn that allowed them to come in because this is the first time that we have come under attack from Boko Haram."'Tactical rapprochement' Until last week, Dapchi had been spared from Boko Haram, even though the group repeatedly attacked Yobe. On January 5, at least nine soldiers were killed in an attack on a military post.That attack was claimed by the Boko Haram faction headed by Abu Mus'ab al-Barnawi, whose leadership is recognised by the Islamic State group.Barnawi's breakaway faction operates over a vast territory in and around Lake Chad and Niger, including Yobe state.Fighters loyal to Boko Haram's long-time leader, Abubakar Shekau, are more active in Borno state and along the Cameroon border.Some analysts said Barnawi, rather than Shekau, was behind the Dapchi attack and may have taken hostages as human shields to mitigate military operations against them.Boko Haram split because of Barnawi's objection to Shekau's use of violence against civilians in the Muslim-majority region, including suicide bombings in mosques and markets."No civilians were harmed (in Dapchi), which is likely a mode of operation of the Mamman Nur faction," said one member of the civilian militia.Nur - Shekau's former right-hand man and the mastermind of the 2011 UN office bombing in Abuja - is seen as the Barnawi faction's de-facto leader."Even in the villages they attacked in the area before Dapchi, they touched no-one, they only looted food supplies," he added.Blurred linesKidnapping remains commonplace for both Boko Haram factions, said St-Pierre."It's very difficult to know who is behind this attack because the factional divisions aren't what they used to be," he added.Both groups had had "tactical rapprochements" and even conducted "joint operations" in recent months, he said.Nigeria media on Monday quoted unnamed local security sources as saying that half of the hostages had been taken to Niger to prevent the Nigerian military from following them.AFP has not been able to verify the claim, although the border is just over 100 kilometres away to the north. Nur, who is believed to have links with Al-Qaeda affiliates in north Africa, is said to have bases on the islands of Lake Chad.Movements of men, arms and equipment have been seen in the border region, without the intervention of either country, making the Boko Haram convoy difficult to detect, said St-Pierre."Whatever the reason, Boko Haram needs women in its ranks and will look to put them in a secure location," he added. "The women have a high value as hostages".