Unknown assailants have shot dead a Yemeni policeman and wounded four others in the country's restive south, a security official said on Wednesday, the fourth such attack in less than a week.

"The gunmen opened fire on a police checkpoint killing one policeman and wounding four others," late Tuesday in the city of Ataq, the capital of Shabwa province, an Al-Qaeda stronghold, the official told AFP.

On March 4, gunmen killed a senior police official in the southeastern province of Hadramawt while the following day unknown assailants shot and wounded a police chief travelling between Aden and the nearby province of Lahij.

Two other policemen were wounded on Saturday when roadside bombs planted in their camp exploded.

Attacks on Yemen's security forces, which officials attribute to Al-Qaeda, have escalated since newly elected President Abdrabuh Mansur Hadi pledged to eradicate extremism and militancy in the country's lawless south and east during his February 25 inauguration speech.

On Sunday, a massive assault on a Yemeni military base in Abyan province blamed on Al-Qaeda extremists killed 185 soldiers.

The extremists, known in Yemen as the Partisans of Sharia (Islamic law) and who have links to Al-Qaeda, seized control of Abyan's provincial capital Zinjibar and several other towns in the south last May as former president Ali Abdullah Saleh faced mass protests.

The violence highlights the security challenges facing Hadi as he tries to restore order and unify the country's armed forces, as stipulated by a Gulf-brokered transition accord that ended Saleh's 33-year rule.