Security officials say an Emirati officer has been killed in a drive-by shooting in Yemen's southern port city of Aden, the sixth assassination of pro-government troop leaders and officials in recent weeks.

The officials said Saturday that gunmen on a motorcycle killed the officer as he entered a store the previous night in Aden.

Although no group has claimed responsibility, pro-government officials say they suspect Sunni extremists. Yemen's al-Qaida is known to have used motorcycles in previous assassinations.

Backed by a Saudi-led coalition that includes the United Arab Emirates, Yemen's internationally recognized government has been at war with Shiite rebels for over a year. Officials say al-Qaida and other extremists have exploited the ensuing chaos.

All officials spoke on condition of anonymity because they are not authorized to brief reporters.