(CNN) -- A militant attack on a government vehicle in Yemen's business capital, Aden, Wednesday, killed a political security officer and injured seven others, three senior security officials said.
The incident happened as the intelligence officers were heading to work. The injured were taken to a government hospital.
Eyewitnesses told CNN that heavy artillery was used in the attack. Security officials blamed al Qaeda.
"This is not the first time intelligence officers were attacked in Aden," said a senior security official who is not authorized to talk to media. "At least 34 have been killed or injured since last September."
A dozen such attacks have taken place in Aden over the last six months, he said.
"We believe that at least four militants were involved in the attack," the official said. "The government will not give additional details before the investigation is complete."
Large explosions were heard in Aden earlier in the day, however no casualties were reported.
Political experts have long doubted that al Qaeda is behind the attacks despite the government claims, and instead believe that members of the old regime are to blame.
"The government has been practicing a dangerous tactic by weakening the political security because its loyalty is not to the ruling family," said Abdul Salam Mohammed, Chairman of Abaad Strategic Center. "These attacks were expected and many others will follow."
Ansaar al-Sharia, an extremist militant group in neighboring Abyan province, has been clashing with government troops for nine months.
It controls large areas of the province after security forces evacuated from a number of its military bases there last year.
Ansaar al-Sharia has threatened to take over Aden and announce a crescent shaped Islamic emirate in south Yemen.