ADEN, Yemen, March 5 (Xinhua) -- Unidentified gunmen on Monday shot dead a senior official of security forces in Yemen's southern port city of Aden, a local police source told Xinhua.

Colonel Abdul Kareem, a commander of the newly-recruited Yemeni security forces in Aden, was killed when gunmen opened fire at him in Sheikh Othman neighborhood, the source said on condition of anonymity.

"The Colonel was assassinated by two masked gunmen riding a motorcycle while he was having his breakfast in a cafeteria in the same neighborhood," the source said.

Yemeni security forces arrived at the scene after the attack and launched an investigation into the incident, the source added.

The incident occurred just 24 hours after the Islamic State (IS) group claimed responsibility for killing two security personnel in Aden.

Commanders of the newly-recruited Yemeni security forces backed by the United Arab Emirates (UAE) are frequently targeted by suicide bombers or drive-by shooters.

No group has claimed responsibility for Monday's drive-by shooting yet, but both the Yemen-based al-Qaida branch and the IS conducted a number of similar attacks in Aden in recent weeks.

The southern port city of Aden is considered as Yemen's temporary capital and the Saudi-backed Yemeni government based itself there since 2015.

During the past two years, the al-Qaida in the Arabian Peninsula (AQAP) and other terrorist groups including the IS had an active presence in Yemen's southern part.

The impoverished Arab country has been locked into a civil war since the Iranian-backed Shiite Houthi rebels overran much of the country militarily and seized all northern provinces, including capital Sanaa, in 2014.

Saudi Arabia leads an Arab military coalition that intervened in Yemen in 2015 to support the government of President Abd-Rabbu Mansour Hadi after Iran-backed Houthi rebels forced him into exile.

The United Nations has listed Yemen as the country of the world's number one humanitarian crisis, with seven million Yemenis on the brink of famine and cholera causing more than 2,000 deaths.