Updated

Tens of thousands of Yemenis took to the streets Thursday to demand dismissal of members of the country's former regime from top military posts, a key to fighting al-Qaida, as 20 militants and Yemeni troops were killed in clashes in the south.

Rallies organized by youth groups were held in the capital, Sanaa, and several other cities. Protesters carried banners urging Yemen's new president, Abed Rabbo Mansour Hadi, to "purge the army of family members" of his predecessor, Ali Abdullah Saleh.

After a year of uprising and turmoil, Saleh handed power to Hadi in February, but several Saleh loyalists and relatives are hanging on to key military posts and refusing to step down.

Saleh has been accused of meddling in the country's affairs and obstructing efforts by Hadi to carry out much-needed reforms.

The U.N. envoy to Yemen, Jamal Benomar, has been meeting Saleh's family members to try to persuade them to comply with Hadi's orders. He said Thursday that a Saleh crony has finally agreed to hand over command of the elite Republican Guard.

Hadi has made restructuring the Yemeni armed forces his top priority, essential in combatting al-Qaida forces in the south.

Islamic militants linked to the terror group have taken over several towns in the south during Yemen's long political and security vacuum.

In the latest battle, the Defense Ministry said Thursday that eight al-Qaida militants and three troops were killed in clashes in Zinjibar, the provincial capital of Abyan province. The military has taken over several parts of the city, an al-Qaida stronghold.

In the nearby town of Lawder, nine al-Qaida militants were killed in a battle when the militants tried to re-enter the town after it was taken by army with help of armed civilians and tribesmen, witnesses said.

Al-Qaida in Yemen, has been linked to several attempted attacks on U.S. targets, including the foiled Christmas Day 2009 bombing of an airliner over Detroit and explosives-laden parcels intercepted aboard cargo flights last year.

Unlike other al-Qaida branches, the network's militants in Yemen have sought to gain a territorial foothold in lawless areas, mainly in the south of Yemen.