Al Mukalla, Yemen - The ongoing expansion of northern Yemen's Houthi rebels has prompted many tribes in the restive south to pull together, despite the rebels' assurances that they will not raid the south.

The Houthis, also known as Ansar Allah, have continued to expand their area of influence since taking control of the Yemeni capital on September 21. The rebels reached the closest point to the south when they seized the province of Baydha on February 10; subsequently, anxious tribes within the borders of the formerly independent south began staging public gatherings.

This week, hundreds of members of the Bani Hilal tribe flexed their muscles in a military parade in the southern province of Shabwa, days after another powerful tribe displayed its arsenal in the same province.

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According to a spokesperson for Bani Hilal, the latest gathering - during which tribespeople lined up dozens of cars loaded with armed men and weapons - aimed to send a message to the Houthis and al-Qaeda that the tribe was ready to resist any possible incursion.

"The aim of this parade is to get ready to confront any force that could target Shabwa in particular and the south in general," spokesperson Naji Al Asami Al Hilali told Al Jazeera. "We wanted also to send a message of solidarity and cheer to President Abd-Rabbu Mansour Hadi over his arrival to Aden."

Hadi had been under strict house arrest by the Houthis for a month when he broke free last week, fleeing to Aden. As the Houthis threatened to try him for treason, some southern tribes expressed solidarity and vowed to defend him if the Houthis were to chase him to Aden. "We assigned some members of the tribe to travel to Aden to meet President Hadi [and] show solidarity with him," Al Hilali said.

By the end of the day, Bani Hilal approved forming an army of at least 10,000 armed men and 400 vehicles to defend the province from intruders.

On February 19, the powerful Al Awalik tribe got together in the same province for the same purpose, bracing for any possible incursion of Houthis into their territories. Al Awalik said they would form an army of 3,000 men equipped with 200 armed vehicles.

Also in the south, tribespeople from the Yafae tribes in Abyan province have been on high alert since the Houthis stormed the neighbouring Bayda province. Armed men have positioned themselves on the mountains, with weapons aimed near the border.

Commenting on the sporadic tribal gatherings, Brigadier Thabet Hussein, a military analyst from the south, told Al Jazeera that the tribes were taking these defensive measures merely to scare the Houthis, who do not appear to be seriously contemplating an incursion into the south.

"These are defensive measures aimed at repelling any attack on their territories. Different factions in the south would act together if [they perceived a threat from the Houthis]," Hussein said. "The Houthis have not declared any aggressive behaviour towards the south."

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But as the tribes in Shabwa displayed their firepower, al-Qaeda fighters appeared to be in the wings, waiting for any chance to recapture some territory in the province. Yemen's branch of al-Qaeda in the Arabian Peninsula (AQAP) capitalised on the central government's struggle with its adversaries during the youth-led protests of 2011, ultimately gaining control of a large swath of land in Shabwa and Abyan. It took the army and allied militiamen months to defeat them and regain control of the cities.

Earlier this month, AQAP re-emerged again when its fighters seized an army base in the province of Shabwa.

Many people use al-Qaeda as a scarecrow to maintain their occupation of the south. Brigadier Thabet Hussein, military analyst

In the south, where conspiracy theory is rife, Al Hilali does not believe al-Qaeda is as dangerous as the Houthis. "The threat of al-Qaeda is overstated," he said. "There is some collaboration among some security officials to allow al-Qaeda to control the base to create a rationale for the Houthis to enter Shabwa."

Officials have repeatedly denied such claims, which are common in the south; Washington has also accused the Houthi-aligned former President Ali Abdullah Saleh of using al-Qaeda operatives to carry out attacks in a bid to weaken Hadi.

According to Hussein, however, "the tribes are able to defeat al-Qaeda. For example, they managed to drive militants out of Abyan and Shabwa in 2012. Many people use al-Qaeda as a scarecrow to maintain their occupation of the south."

Despite the tense mood in the south, the Houthis have said they have no intention to push into that territory. Mohammed Al Magalih, a member of Houthi Revolutionary Committee that governs rebel-controlled regions, said they would leave Hadi and his men to run the south while they worked on building state institutions in the capital.

"The armed forces and the popular committees would not intervene in people's affairs in the south and would not have any security or military presence there," Al Magalih said in a recent post to his Facebook page. But the Houthi leader did not rule out the possibility of entering the south if the "people of Aden" asked for a rescue from pro-Hadi militiamen, or if al-Qaeda were to take control of the south.