The U.N. envoy to Yemen met Monday with the country's ex-president to press him to stop meddling in the country's affairs, diplomats said, a sign of continuing political instability that has emboldened al-Qaida.

The meeting between U.N. envoy Jamal Benomar and the former leader, Ali Abdullah Saleh, came after his son appointed a relative to head a new security unit, defying orders from the current president.

In February, Saleh handed power to his deputy, Abed Rabbo Mansour Hadi, in an internationally backed agreement.

Since then, Saleh has been accused of obstructing Hadi's attempts to purge Saleh's loyalists from security agencies.

The internal conflict, marked by huge demonstrations against Saleh and violent government repression, has been going on for more than a year. During the political turmoil, al-Qaida-linked militants have taken over parts of the south.

Hadi's new government has launched a wide offensive in the region, setting off battles that have taken high casualties on both sides.

On Monday, military officials said 17 al-Qaida militants were killed in a two-pronged attack by military units and civilians who took up arms against al-Qaida south of the town of Lawder. The officials said two civilians and a military officer were also killed in the fighting.

The officials spoke on condition of anonymity because they were not authorized to speak to reporters.

Hadi has vowed to make the battle against al-Qaida a priority. He stepped up the offensive against the militants in the south after a military shake-up to replace Saleh loyalists with new commanders. Saleh and his close aides have repeatedly defied Hadi's orders, frustrating some of his efforts.

In the latest power struggle, Ahmed Ali Abdullah Saleh, son of the former president, appointed a relative, Tarek Mohammed, to head his father's security unit in direct defiance of an order from Hadi. The younger Saleh commands the powerful Special Forces and Republican Guard, among the country's best trained troops.

Hadi had earlier demoted Mohammed from head of the Presidential Guards to commander of a provincial military unit, but Mohammed and Saleh refused to carry out the order. Mohammed's refusal to hand over his current post came during a meeting attended by the U.N. representative to Yemen.

Two diplomats said the U.N. envoy, Benomar, met ex-President Saleh in a last-ditch attempt to persuade him to implement Hadi's orders.

The diplomats said the U.N. envoy told Saleh he will raise the issue at the U.N. Security Council, warning of sanctions against his loyalists. The diplomats were speaking on condition of anonymity to discuss the private conversation.

Saleh's response was not known.