Tensions in southern Yemen escalated on Monday after the UAE-backed Southern Transitional Council seized control of parts of the oil-rich Hadhramaut province.

In response, Yemen’s airspace was briefly closed, stranding hundreds of passengers, as the Saudi-led coalition reportedly withheld flight permissions to send a “message” to the separatists.

The takeover highlights divisions within the anti-Houthi camp, which opposes Iran-backed Houthis controlling most of northern Yemen, including the capital, Sanaa.

The Southern Transitional Council seeks an independent southern state, raising fears that Yemen could split after over three decades of unification, the AP has reported.

Saudi Arabia, which has controlled Yemen’s airspace since entering the war in 2015, did not officially confirm the closure.