KIRKUK, Iraq, April 13 (Reuters) - Christians at the cathedral in the northern Iraqi city of Kirkuk said on Sunday their prayers for peace had been answered, but what comes after the fall of Saddam Hussein is what worries them now.

At the first mass for Iraq's Chaldean Catholic minority since government forces collapsed on Thursday and U.S. troops moved in, Bishop Andraus Sanna said in a sermon delivered in Arabic that his flock had much to be grateful for.

But having enjoyed relative religious freedom under Saddam and his Baath party, Christians feel they have something to lose now he has been ousted from power and U.S. forces promise democracy in a largely Muslim country.

"The situation is not stable," said Ghada Abbo, a doctor.

"We do not have any idea what will happen to us in the future," she added, looking up as U.S. B-52 bombers circled high in the sky.

Iraqi headquarters and military positions in and around the oil-rich city of 700,000 people were pounded from the air during the last few weeks, and government forces eventually collapsed.

Hundreds of Kurdish "peshmerga" fighters poured into the city amid scenes of jubilation, but the atmosphere quickly soured when looting and lawlessness began, some of it blamed on the Kurds themselves.

"This is the second time the Kurds have done this," said S. G. Alhurmazi, a retired oil worker, sharing the view of many in Kirkuk.

"The last time was in 1991," he added, referring to a Kurdish uprising after the last Gulf War that was brutally repressed.

ETHNIC TENSION


Tens of thousands of Kurds have been forced to leave Kirkuk by Saddam's policy of Arabisation, and Turkmen and Arab communities in the city fear violent reprisals.

So far they have not materialised, and the vandalism of Thursday and Friday has died down as the U.S. military presence in the city grows. But not even U.S. military might is enough to guarantee stability in the long term.

"The Americans won't be here forever, will they?" said Alhurmazi.

In his house opposite the cathedral, 83-year-old Sanna said he did not expect Christians to be persecuted or sidelined, despite what some other Iraqis consider their cosy relations with the Baath party.

There were fears during the buildup to the war on Iraq that the tiny Christian minority, numbering an estimated 600,000 people in a country of 26 million, could suffer a backlash from those who considered them allies of Saddam.

"No one was really with the Baath party here, and Muslims know that," said the bearded cleric, dressed in black and mauve robes and skullcap. "Many people may have belonged to it, but that was because they needed to be in order to get jobs."

Speaking in French, he explained the outbreak of vandalism and looting in Kirkuk after the fall of Iraqi forces as a natural reaction by Kurds to the repression they had suffered at the hands of Saddam and his regime.

Sanna was optimistic that Kirkuk could avoid the kind of ethnic violence and lawlessness that has hit Mosul, another oil-rich city in northern Iraq, since it fell this week.

But risks remained in Kirkuk, where Arabs, Kurds and Turkmens eye each other with suspicion.

"The Turkmens fear the Kurds, and they are encouraged to voice these concerns a little by Turkey," Sanna said. "And the Arabs feel a little dejected at the moment. They are afraid of the Americans."

Iraq's Christians say their roots go back to the first century when the apostle Thomas evangelised Iraq, which was then Mesopotamia. An estimated 65-70 percent of them are Chaldeans, an old Catholic sect that originated in Iraq.