A 400-strong Sudanese force arrived in Yemen's port city Aden Monday in support of pro-government forces preparing to confront a possible new offensive by rebels on the country's south.
Yemen's loyalist forces, backed by Saudi-led coalition strikes, supplies and troops, pushed the rebels out of Aden as part of an operation launched in July to take back territory they had lost.
Four other southern provinces -- Lahj, Daleh, Abyan and Shabwa -- were also retaken by the forces loyal to President Abedrabbo Mansour Hadi.
But the Iran-backed rebels this weekend recaptured several positions in the south.
"More than 400 Sudanese soldiers landed in Aden" as part of the coalition battling the rebels since March, said a commander of pro-Hadi forces.
They will join 500 Sudanese soldiers who arrived in Aden on October 19. Some of them were deployed in the southern port and the strategic Al-Anad airbase in adjacent Lahj province, the source said.
Their arrival comes as loyalist forces are mobilising to block a possible attempt by the rebels to re-enter Aden.
"General mobilisation was been declared in Daleh" province where rebels recaptured second city Damt on Saturday, a local official said.
A similar call was made in the coastal city of Dhubab, where the rebels achieved a "limited advance" during the weekend, a military source said.
The rebels seized a military base in Dhubab on Saturday following deadly clashes with pro-government troops, according to military sources.
Pro-government troops seized Dhubab early last month, giving them effective control of Bab al-Mandab, through which much of the world's maritime traffic passes.
The rebels overran the Yemeni capital Sanaa last year and then advanced south to Aden, forcing Hadi and his government to flee to Saudi Arabia.
Ministers from Hadi's government returned to Aden in mid-September after six months in exile in the neighbouring oil-rich kingdom.
The United Nations says that around 5,000 people have been killed in Yemen's conflict since it escalated in March.
Meanwhile, radical Islamist gunmen entered the faculty of administrative science at Aden university, forcing students to leave the campus and locked down the faculty's main gate, witnesses said.
They said the gunmen closed the faculty weeks after they threatened to use force against students if they do not observe segregation of the sexes on campus.
Gunmen last month distributed leaflets also banning music and signed by the Aden and Abyan branch of the Islamic State group.
The threatened to carry out car bomb and petrol bomb attacks if mixing on campus continues.
Islamist militants, including Al-Qaeda and IS, appear to have gained ground in Aden where jihadists are now visibly present.