ADEN : Islamist suspects killed three Yemeni soldiers in two separate shootings in the south on Sunday, officials said, the latest in a spate of attacks on security forces.

In the first attack, two men on a motorbike opened fire on two soldiers eating at a restaurant in the Sheikh Othman district of the port city of Aden, an official said.

The assailants are suspected of belonging to either Al-Qaeda or the Islamic State group, the official said.

Further north, a suspected jihadist on a motorbike shot dead a soldier as he headed home in Sabr village, in the province of Lahj, a security official in the area said.

CIA director John Brennan said this month that IS is now collaborating in Yemen with rivals like Al-Qaeda in their fight against Shiite Huthi rebels and government forces backed by the Arab coalition.

"We see it right now in Yemen... There are indications that, in fact, they're working together," he said.

The Saudi-led Arab coalition launched a military campaign against the Huthis and their allies in March 2015 after the Iran-backed insurgents closed in on President Abedrabbo Mansour Hadi in his refuge in Aden.

After driving the rebels out of Aden and four other southern provinces during the summer, loyalist forces backed by the coalition waged military campaigns to root out jihadists who had exploited the power vacuum to strengthen their footholds in the south.

Fighting in Yemen since March 2015 has killed more than 6,600 people, most of them civilians, and displaced at least three million others, according to the United Nations.