Strife-battered Yemen is sliding deeper into chaos amid a power struggle that's ripping the army apart while U.S. Special Forces and the CIA step up their largely secret war against al-Qaida as it battles government forces for control of the south.

The covert U.S. campaign, waged in conjunction with Yemeni military forces, mainly employs unmanned aerial vehicles flown from the U.S. base at Djibouti, across the Gulf of Aden from Yemen, and a secret base believed to be in Saudi Arabia.

Sometimes, U.S. strike jets are reportedly to be used.

On March 18, the al-Qaida positions in the southern port city of Zinjibar were hit by what Yemeni officials called missile fire from the Gulf of Aden.

The Long War Journal, which monitors global counter-terrorism operations, observed, if missiles were fired, "they were most likely fired by U.S. Navy warships.

"The Yemeni navy does not possess the capability to conduct such strikes; its missile boats and corvettes fire only anti-ship missiles," the Long War Journal said.

The escalation follows the Feb. 27 inauguration of President Abd-Rabbuh Mansour al-Hadi. He was elected in a vote in which he was the only candidate.

He replaced longtime dictator Ali Abdullah Saleh, whom the Americans and the Persian Gulf monarchies eased out after a year of pro-democracy protests in which authorities say 2,000 people were killed.

Unlike Saleh, who often enlisted the help of Islamist hard-liners to stay in power during his 33-year rule, al-Hadi, Saleh's longtime deputy, has made cracking down on al-Qaida a top priority, calling it a "religious and national duty."

There have been 26 reported U.S. drone strikes since May 2011, after U.S. President Barack Obama ordered intensified operations against al-Qaida.

The tempo has accelerated with a dozen so far this year in which scores of jihadists have been reported killed.

Since Hadi's inauguration, al-Qaida has also stepped up operations, so the U.S. escalation should be seen in that light, too.

Yemen's military, despite clashes between Saleh and Hadi loyalists, has taken a beating, losing several bases and some 250 fatalities.

This has detracted from the Sanaa government's counter-terrorism efforts.

But the Americans' vastly improved intelligence-gathering capabilities and Hadi's orders to Yemen's security services, long-suspected of being infiltrated by Islamists, to go after al-Qaida, seems to be paying off.

The U.S. offensive is directed primarily against the southern provinces of Abyan, Shabwah and Bayda, the main stronghold for al-Qaida in the Arabian Peninsula, arguably the jihadist movement's most aggressive branch.

In recent months, AQAP and its local arm, Ansar al-Shariah, have seized several cities and towns and repelled most attacks by government forces to take them back.

Ansar al-Sharia, which played a major role in wiping out some 150 soldiers in a jihadist attack west of Zinjibar, has begun taking over government functions, Taliban style, in towns held by al-Qaida.

Much of the fighting in the south is carried out by local jihadists, led by seasoned al-Qaida veterans, many of whom fought a three-year campaign in Saudi Arabia that was crushed in 2007.

Jaar, just north of Zinjibar and the first city in Abyan the jihadists conquered in 2011, has become AQAP's main bastion where it recruits on a large scale.

Zinjibar, Abyan's provincial capital, fell in May 2011, and was followed by Shaqra, Rawdah and Azzan.

Like much of the south, which was a Marxist state until it merged with North Yemen May 22, 1990, these cities are plagued by heavy unemployment, extreme poverty and illiteracy.

In such a deprived environment, amid the rampant corruption of Saleh's government, these places are breeding grounds for jihadists as they extend control over the south, which became independent in November 1967 after driving out the British in a guerrilla war.

The south has long been neglected and since the 1990 union has been marginalized politically and economically.

That intensified after the south lost a four-month secessionist war with the north in 1994 in which, ironically, Saleh was aided by hard-line Islamists.

Yemen's poorly led security forces pulled out of large swathes of the south a year ago, leaving a vacuum that al-Qaida has filled.

Meantime, it's taking full advantage of Hadi's power struggle with Saleh's loyalists, led by his relatives who still hold key military posts, to make gains.