At least six people are thought to have been killed on Saturday in northern Nigeria, with the military claiming there was an attempted assassination of the country's chief-of-staff.A Nigerian army spokesman accused the Islamic Movement of a "deliberate assassination" attempt of army chief Lt. Gen. Tukur Buratai in Zaria city.The army said hundreds of people laid roadblocks, with Shia gunmen opening fire on a convoy carrying the senior officer.Buratai escaped the incident, in which the army said it acted within its "Rules of Engagement and Code of Conduct".However, the Shia group disputed the army's version of events. It described an "unprovoked siege" on its headquarters by troops and called the assassination claim an afterthought and a "blatant lie"."The attack on the defenseless people by the Nigerian soldiers [was] unprovoked," the movement said in a statement on its website.Although the movement did not confirm the six purported deaths, eyewitnesses told Anadolu Agency that the security forces had opened fire on the group's headquarters."Six members of the Islamic Movement of Nigeria were killed at the Hussainiyah area when soldiers laid siege on their headquarters. This later led to serious protest and confusion in Zaria," said Abubakar Sidi, a resident of Hussainiyah, claimed, adding that nine other people had been injured.Another resident, Tolhat Umar, said soldiers had been seeking a Shia leader, Sheikh Ibrahim El-Zakyzaky, but met with resistance."There was argument and then shooting by both sides. At the last count, six Shiite members died," Umar claimed.The army and the Shia community have had a long-running dispute dating back to 1979.Last year, at least 33 Shia Muslims were gunned down by soldiers in Zaria during an encounter, after which both sides gave contradictory accounts.Earlier this month, dozens died in a suicide attack on a Shia procession near northwestern Kano city. Shia spokespersons later claimed it had been masterminded by the army.