A series of suicide attacks executed by females in Nigeria in the past year has suggested a new trend whereby Boko Haram recruits females as suicide bombers to avoid security measures and surveillance focused on men.

Observers of the Islamist group believe that female bombers appear less suspicious, while some think it easier for females to hide weaponry if they wear baggy clothes.

The latest attack came last Saturday when a young female suicide bomber blew herself up in a busy market near a bus station in Damaturu, leaving at least seven people dead.

Earlier in May, four female bombers killed six vigilante militia members and three soldiers near the Giwa military barracks in Maiduguri.

In 2014, Nigerian military spokesperson Onyema Nwachukwu confirmed that Boko Haram had a "female wing" whose main tasks were to spy for the group and to recruit potential wives for men on the frontline.

Nigerian authorities were able to free more than 500 abducted girls, who some speculate might have been groomed as suicide bombers.

With female suicide terrorism surging, the advantage decreased as security services took measures to deal with it, Elizabeth Pearson, a journalist focusing on the kidnapping tactics of Boko Haram, told Ahram Online.

"Nowadays, especially in Nigeria, women are increasingly put under the radar, along with men," Pearson said.

Are girls offered an "incentive"?

Some argue that females are forced to turn into human bombs, while others suggest they are offered incentives of money, promises of bliss in the afterlife, or run after the dream of an Islamic Caliphate in place of the "corrupted Nigerian state."

Given the poor families most of these girls come from, a financial reward stands as an attraction, Chika Oduah, a Nigerian journalist reporting on the cases, told Ahram Online.

In March, Boko Haram declared allegiance to the well-funded Islamic State (IS) militant group, which controls large swaths of Syria, Iraq and Libya. Some of Boko Haram's recent videos resemble the high-quality videos of IS.

The biggest prize, however, stems from the religious cause, Oduah argues, where Boko Haram militants convince recruits that killing civilians deemed infidels would guarantee them a place in heaven.

Both financial and religious “incentives” are used by extremist groups when recruiting male suicide bombers, and are not exclusive to female recruits.

Sometimes not much convincing is needed, when the women are wives and daughters of Boko Haram fighters. Last summer, authorities arrested women who had deliberately been engaged in attacks, including Hafsat Bako, who was married to a Boko Haram commander.

Little is known about the arrested militants after their detention.

Brainwashing is not always the case; sometimes parents of females pressure them into action.

"We had the testimony of Zaharau Babangida, who said her parents pushed her to carry out an attack … which she ultimately refused to do," Pearson said.

Thirteen-year old Babangida said her father told her to prepare to die as a martyr and clear the way for him to join her soon, the Nigerian newspaper Vanguard News reported in December.

Graph showing number of female suicide bombings in Nigeria from June 2014-March 2015 (Photo:Courtesy of Washington based organization Fund for Peace).

Speculation bombers are Chibok girls

Speculation has gone viral on social media that some of the Nigerian schoolgirls kidnapped in April 2014 may have been forced to become suicide bombers.

Some of the over 276 female students abducted from the government secondary school in the town of Chibok remain missing, adding to the speculation.

"(But) there is no solid evidence that the kidnapped girls are themselves the female suicide bombers," Oduah said.

Former Nigerian Education Minister Oby Ezekwesili in July 2014 expressed fears such speculation may carry weight, urging the Nigerian government not to "move on" as the Chibok girls may be "indoctrinated or coerced into being used as suicide bombers," International Business Times reported.

"Female suicide bombers are again and again becoming the trend and our Chibok girls are still in the enemy's den. It worries me." Ezekwesili added.

The Human Rights Writers Association (HURIWA) also urged the government to investigate the identity of female suicide bombers.

"Nigerian security forces release little information," Oduah said, adding that the information made known was mostly revealed by reporters in the field.

Testimonies of some of the kidnapped girls who spoke to Oduah revealed that Boko Haram has been training the Chibok girls, though to what end remains unclear.