Police said on Wednesday they had restored calm after fierce fighting between ethnic Ijaws, their Itsekiri rivals and security agents.
"A combined team of soldiers, navy and police are patrolling the flashpoints, particularly the McIver and port areas, to ward off possible attacks by Ijaw youths," a police official said.
He added sporadic shooting was heard overnight but no major incidents were reported.
Delta State Governor, James Ibori, was due on Wednesday to hold a meeting with the warring parties and security forces in the war-weary town.
Ibori's spokesman Sheddy Ozoene said delegates had begun arriving and would begin meeting shortly.
"It is going to be an enlarged peace meeting involving all the security agents - police, army, navy and air force - and leaders of the various ethnic groups in Warri," he said.
"We have directed our staff to be careful about their movement in and around Warri to avoid unpleasant circumstances"
Chevron Texaco spokesman
Ozoene said the governor hoped the talks would finally resolve age-old rivalries over land rights among the three main ethnic groups - Ijaw, Itsekiri and Urhobo - in the oil city.
The world oil market is already jittery over the crisis in Warri, home to much of Nigeria's multi-billion-dollar oil and gas wealth.
Anglo-Dutch oil giant Shell, which accounts for a third of Nigeria's output of two million barrels per day, has ordered its workers in the troubled town to stay at home.
But a company spokesman said on Wednesday oil production had not been affected.
Another big oil player, ChevronTexaco, said it was was studying the situation cautiously.
"We have directed our staff to be careful about their movement in and around Warri to avoid unpleasant circumstances, but I can assure you that production is going on in the swamps. No disruptions at all," an official said.