(Adds latest fighting, quote, context)
By Mohammed Mukhashaf
ADEN, Aug 8 (Reuters) - Southern separatists and presidential guards fought for a second day on Thursday in Aden, the seat of Yemen's government, with at least one person killed, residents said.
That followed three deaths and nine injuries when gunfire erupted between the rivals on Wednesday, complicating efforts to end a more than four-year war that has killed tens of thousands and pushed Yemen towards famine.
The separatists are nominally allied with President Abd-Rabbu Mansour Hadi in a Saudi-backed coalition battling the Iran-aligned Houthis. But they have rival agendas for Yemen and the separatists accused a Hadi-allied party of complicity in an attack last week on their soldiers.
After Wednesday's funeral for some of the troops killed in that missile strike on a parade, separatist supporters fought with guards near the hilltop presidential palace in the Crater district of the southern port city, witnesses said.
Thursday's fatality came when fighting flared again and a stray bullet hit a man walking in the street, witnesses and his relatives said. Sounds of gunfire and heavy weaponry echoed into the evening while smoke and fire could be seen rising.
With Hadi in Saudi Arabia, the palace is largely empty.
The two days of violence in Aden come after coalition member the United Arab Emirates, which has armed and trained southern separatist groups, said in late June it had begun to withdraw forces from Yemen.
Two Yemeni officials told Reuters that Saudi troop and vehicle reinforcements arrived in Aden on Thursday, continuing a build up of Saudi forces in areas vacated by the UAE.
Media outlets affiliated with the Southern Transitional Council (STC) separatists said on Thursday their leader Aidaroos al-Zubaidi had flown into Aden from his home in the UAE.
"It is very unfortunate that the people of the south are fighting among themselves," Aden resident and university worker Mohammed Ahmed al-Arshi told Reuters.
"We hope that everyone is aware of the dangers and impact of any new civil wars because people have had enough of what happened in previous wars." (Reporting by Reuters team in Yemen Writing by Lisa Barrington Editing by David Holmes and Andrew Cawthorne)