Saudi-led warplanes hit anti-government forces in south Yemen Monday, killing at least 12 Shia Houthi insurgents and allied forces as fighting continued across several provinces, military and local sources said.

Coalition aircraft pounded five schools converted by rebels into military bases in Ataq, the capital of Abyan province, military sources said.

The raids killed at least 12 Houthi rebels and troops loyal to former president Ali Abdullah Saleh, who has allied himself with the northern insurgents against the government of President Abedrabbo Mansour Hadi, the sources said.

Also in Abyan, warplanes targeted rebel positions on the outskirts of Loder, the province's second largest city, witnesses said.

Clashes were ongoing southwest of Loder between rebels and southern forces that have sided with Hadi, they added.

Fierce fighting also raged in the central city of Taez, with the warring parties using tanks and rocket-propelled grenades inside residential areas, local officials said.

Medics said at least 16 civilians were killed in Taez on Sunday. Coalition warplanes meanwhile hit rebel positions east of Taez overnight, witnesses said.

The United Nations says more than 1,000 people have been killed in fighting in Yemen since late March, when Saudi Arabia assembled an Arab coalition in support of Hadi.

The embattled leader asked for Gulf intervention after the rebels closed in on his refuge in the southern port city of Aden after they had overrun several provinces since September, including the capital.

He has since fled to Saudi Arabia.

Air strikes have continued despite a coalition announcement last week of an end to its air campaign dubbed "Operation Decisive Storm".