Washington has made the targeted killing of jihadist leaders the central tactic in its war on extremism, but experts say drone strikes alone do not amount to an effective strategy.

On Tuesday, the White House boasted that the death in a presumed CIA drone strike of Nasir al-Wuhayshi, Al-Qaeda's franchise leader in Yemen, was a "major blow" against the network.

The strike followed hard on the heels of the apparent death of Sahara warlord Mokhtar Belmokhtar in a US air strike on a gathering of Al-Qaeda-linked figures in eastern Libya.

But previous US assassinations have failed to halt the advance of jihadist extremism in the region, and it remains far from clear whether tactical success leads to strategic victory.

Nick Heras of Washington think tank the Center for a New American Security said Al-Qaeda in the Arabian Peninsula (AQAP) might even emerge stronger after al-Wuhayshi's demise.

AQAP is considered the Al-Qaeda franchise that currently poses the greatest threat to Western targets, and the chaos of Yemen's civil war has given it a chance to grow.

"It's very possible that AQAP could emerge after this targeted killing, if not in a stronger position, with the same general movement," Heras told AFP.

AQAP, which was behind several plots against Western targets including the attack on French magazine Charlie Hebdo, quickly named military chief Qassem al-Rimi as its new leader.

Heras said Rimi "is believed to be even more of a leader that has a focus on targeting the West from the Yemeni Al-Qaeda base.

"He is also considered to have a mind for logistics. A leader that is perhaps less charismatic but more effective."

Thus, Heras warned, the vaunted US strike could have the "potential secondary effect of making AQAP down the line more effective."

A targeted killing "does not remove the entire organizational structure... it weakens control over territory but can't remove AQAP from the areas of Yemen that it controls."

- Ground combat -

Al-Qaeda remains a threat even after the May 2011 killing by US Navy SEALs of its leader Osama bin Laden.

And the Islamic State group emerged out of the remains of Al-Qaeda's Iraqi franchise even after US bombs killed founder Abu Musab Al-Zarqawi and many other leaders were jailed.

In fact, the extremist groups in Syria may have received a boost in 2014 when US bombings targeting militants in the northwest of the country killed community members.

Heras argued that these strikes "caused a lot of outrage" and led to "a collapse of the influence of the US-supported groups."

Not surprisingly, US officials have a more upbeat view of their recent successes.

Pentagon spokesman Colonel Steve Warren said the strikes showed that even though US troops have no ground combat presence in the region, Washington can still hurt its enemies.

"Even though we do no longer have a presence in Yemen, we don't have a presence in Libya, we still have a global reach," he said.

"We still retain the ability to find and kill terrorists wherever they are hiding in the world."

And a senior State Department official said: "I wouldn't predict any future strikes in any geographic area, but I can tell you that being a member of Al-Qaeda is a career choice that definitely has a shelf life here."

Emily Schneider, a senior associate at the international security program of think tank New America, dubbed the recent strikes a success, but warned: "If that's a successful strategy remains to be seen.

"New leaders may not be as smart or they could be a little more agile, younger and open to use new sources to recruit."