Al-Qaida-linked militants fired mortars into a southern Yemeni town, killing two children, while government air raids killed six militants in another part of the town Wednesday, the Defense Ministry said.

Militants have been battling the Yemeni security forces for weeks over control of Lawder, a strategically important town in Abyan province.

The Defense Ministry said the air raids in Lawder killed six al-Qaida-linked fighters.

The militants have taken advantage of more than a year of internal turmoil in Yemen to take over extensive territory in the country's south.

Lawder lies on a key highway linking Abyan province's capital of Zinjibar, an al-Qaida stronghold, with other provinces further east, where the group is also active. Militants earlier controlled Lawder but residents chased them out in July. Since then, militants have been trying to regain their foothold in the town, which has a population of about 30,000.

Security officials said militants fired mortar rounds into the city later Wednesday, destroying five houses and killing two children. The officials spoke on condition of anonymity because they were not authorized to speak to reporters.

A local resident, Mohammed Qassim, said the children were under 10 years old.

The violence came as the U.N. envoy to Yemen arrived in the capital, Sanaa, to back Yemen's new leader, President Abed Rabbo Mansour Hadi.

Hadi has been trying to purge the security forces of holdovers from former President Ali Abdullah Saleh's regime.