Unknown gunmen shot dead a security officer in Yemen's temporary capital the southern port city of Aden on Wednesday, local officials said, two days after the government returned in order to assume its duties from the city following months of exile in Saudi Arabia and the UAE.

Using a motorbike, the gunmen shot Colonel Abdulsalam Salim Saad in the district of Al-Mansoura, they said, adding that the officer died immediately and the gunmen ran away before the authorities arrived at the scene.

On Tuesday, unknown gunmen killed  Mohammed Al-Tamimi, a businessman,  in an unprecedented incident in the city which has been facing huge security challenges since it was liberated from the Houthi militants in mid-2014.

Al-Tamimi was shot near his house in Al-Mansoura where most of the targeted killings have been reported.

Besides targeted killings, Aden has also been experiencing presence of militant groups such as Al-Qaeda and ISIS. ISIS has claimed deadly blasts targeting officials including the former governor of Aden.

No arrests have been made in connection with assassinations and blasts.

Meanwhile, the officials said more forces arrived today to help the government forces boost security and restore stability in Aden as well as providing assistance to the government forces fighting the Houthi militants in other regions including Taiz.

The coalition has recently deployed thousands of Arab troops and Yemeni troops trained in GCC states to help the government secure the cities retaken from the Houthis.

The coalition, which has been bombing Yemen since March, helped the government forces drive the Houthis out of southern regions last year.