ADEN (Reuters) - Southern separatists seized most Yemeni government security and military bases near the port of Aden on Tuesday after clashes between nominal allies that have complicated U.N. peace efforts, residents and officials said.

FILE PHOTO: Members of UAE-backed southern Yemeni separatist forces stand by a military vehicle during clashes with government forces in Aden, Yemen August 10, 2019. REUTERS/Fawaz Salman/File Photo

The separatists and the Yemeni government are both part of a Saudi-led military coalition battling the Iran-aligned Houthi movement, which took over the capital Sanaa in the north and most major cities in 2014.

But the separatists broke with the government when they seized its temporary base of Aden on Aug. 10.

On Tuesday, they took over military police, special forces and military brigades camps in Zinjibar, around 60 km (40 miles) east of Aden in Abyan province, local officials said.

This effectively put control of the Abyan capital in the hands of the United Arab Emirates-backed separatists, who seek self-rule in the south, and further weakened the government of Abd-Rabbu Mansour Hadi, who resides in the Saudi capital Riyadh.

The Saudi-led military coalition, which backs Hadi, carried out air strikes on Zinjibar, two sources including a local official said.

“What is happening in Abyan is an unjustified escalation by the Southern Transitional Council (STC - the separatists),” Hadi’s Foreign Ministry said in a statement.

STC president Aidaroos al-Zubaidi headed with a delegation to the Saudi city of Jeddah late on Tuesday after accepting the kingdom’s invitation to a summit on the crisis in Aden, the council said.

Yemeni sources have said the summit could reshuffle Hadi’s government to include the STC.

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The violence and cracks in the coalition are hampering U.N. efforts to advance peace deals elsewhere in the country and talks to end a war that has killed tens of thousands and driven the Arabian Peninsula country to the brink of famine.

In northern Yemen, the Saudi-led coalition said it carried out air strikes overnight on Houthi military targets in Sanaa. The coalition said its air strikes pounded caves storing missiles, drones and weapons.

The assault appeared to be a response to Houthi attacks on energy assets in neighboring Saudi Arabia on Saturday.

The Western-backed, Sunni Muslim coalition intervened in Yemen in March 2015 against the Houthis, who ousted Hadi’s internationally recognized government from power in Sanaa.

Divisions have spread, with the war - widely seen as a proxy conflict between Saudi Arabia and Shi’ite Muslim regional rival Iran - largely mired in stalemate.

STANDOFF

The STC said its forces would hold Aden until the Islamist Islah party, a backbone of Hadi’s government, and northerners were removed from power positions in the south.

The standoff has exposed differences between allies Saudi Arabia and the UAE, which in June scaled down its presence in Yemen but still backs thousands of southern separatists.

STC fighters seized Aden after accusing Islah, which the UAE regards as an offshoot of the Muslim Brotherhood, of being complicit in a Houthi missile assault on southern forces earlier this month, an accusation the party denies.

The separatists’ seizure of bases in Abyan, Hadi’s birthplace, showed they are holding firm to demands to govern the south and be included in shaping Yemen’s future.

“For too long the southern voice has been excluded from any negotiation table,” STC said in a statement to the U.N. Security Council ahead of a Yemen briefing on Tuesday in New York.

“The onus is now on the international community, and in particular the U.N. Security Council, to accept the new realities on the ground.”

The government, in a letter to the Security Council, reiterated a call on the UAE to stop backing separatist forces.

U.N. envoy Martin Griffiths, speaking in New York, said the fragmentation of Yemen risked “becoming a stronger and more pressing threat” if the situation in the south continued.

The separatists, who accuse Hadi’s government of mismanagement, aspire to revive South Yemen - which was a separate country before unification with the north in 1990.

The Houthis, who say their revolution is against corruption, point to Aden as proof that Hadi is unfit to rule.

They are also trying to raise their profile, visiting Tehran last week where they met with European diplomats. They also named an envoy to Iran, and Iran appointed one in return.