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The Yemeni army is gearing up for a push to try to take a southern coastal town from al-Qaida-linked fighters, local residents say.
Via text message, the head of the southern military zone asked people living in the area not to use the roads around Shaqra and two other towns controlled by the fighters.
Shaqra lies on Yemen's southern coast, along a major shipping route that is also the gateway for Somali fighters entering the country.
Al Jazeera's Hashem Ahelbarra, reporting from the frontline in the southern town of Zinjibar, the capital of Abyan province, said on Monday: "The army has taken up positions here. They are backed by thousands of tribal fighters, air force and drone attacks.
"The problem they say [they face] is al-Qaida using guerilla warfare tactics making it extremely difficult for the Yemeni army to put an end to the presence of al-Qaida, which has gained more territory in the southern part of Yemen."
The U.S. is backing the offensive in the south and has stepped up its campaign of drone strikes on alleged al-Qaida members.
It has also sent dozens of military trainers and stepped up aid to Yemen where it wants President Abd-Rabbu Mansour Hadi to reunify the military and fight al-Qaida's Arabian Peninsula (AQAP) wing.
Speaking to Al Jazeera near the frontline, army Colonel Ali Radman Qahtan said: "The biggest challenge we face is that al-Qaida fighters are constantly on the move in small numbers, they never hold out in one place.
"It's an army fighting militias, they know the area very well ... and take advantage of the dense trees to move surreptitiously."
The army also clashed with AQAP in the town of Jaar, about 30km to the north.
Meanwhile, hundreds of troops backed by tanks were closing in on the AQAP-held town of Shaqra, about 50km along the coast east of Zinjibar, residents there said.