KIEV, Ukraine — Pipeline diggers unearthed a mass grave believed to contain thousands of Jews slaughtered in Ukraine during World War II, a Jewish community spokesman said yesterday, a grim finding in a nation that one Holocaust expert described as “an enormous killing field.”

The grave was found by chance last month when workers were laying gas pipelines in the village of Gvozdavka–1, about 110 miles northwest of the Black Sea port city of Odessa, said Roman Shvartsman, a spokesman for the regional Jewish community.

The Nazis established two ghettos during World War II near the village and brought Jews there from Odessa and what is now the nation of Moldova, Mr. Shvartsman said.

In November 1941, Nazi officials set up a concentration camp in the area and killed about 5,000 people.

“Several thousand Jews executed by the Nazis lie there,” Mr. Shvartsman told the Associated Press.

The Jewish community was aware of the mass murder at the time, but no one knew where the bodies were buried, he said.

Yitzhak Arad, a Holocaust scholar and a former director of the Yad Vashem Holocaust Museum in Jerusalem, said the area was known to be a site of mass killings of Jews during the Holocaust. He said he found that 28,000 Jews were brought there from surrounding towns and that 10,000 died — murdered at a rate of around 500 a day.

Holocaust expert Efraim Zuroff, director of the Israel office of the Simon Wiesenthal Center, said the discovery was not unexpected.

“I’m not surprised that, even in these days, there are discoveries such as these. It underscores the enormous scope of the plans of annihilation of the Nazis and their collaborators in Eastern Europe,” he said.

Hundreds of mass graves exist in Ukraine, and many have not yet been discovered, Mr. Zuroff said. “Ukraine was an enormous killing field, hundreds of thousands of Jews were murdered,” he said.

About 240,000 Jews were killed by the Nazis in the Odessa region, which was occupied by the German-allied Romanians, according to Mr. Shvartsman.