MOSCOW - A Russian news agency found out yesterday that jokes about Soviet domination aren't such a hoot in Eastern Europe - even on April Fools' Day.

ITAR-Tass, which traditionally runs gag items on April 1, reported that Russia's parliament was planning to consider reviving the Warsaw Pact military alliance of former Soviet allies in Eastern Europe.

The legislation, it said, would be a ''secret weapon'' aimed at ruining the expansion plans of NATO, the pact's former arch-foe.

Other than the word "April" in the story's title, there was no tip-off that it was a joke. Taking it for serious news, state-run news agencies in the Czech Republic and Bulgaria picked up the story immediately and it was broadcast on national radio at least twice in each country.

Seven hours later, ITAR-Tass ran a straight news story on the reaction to its story as an ''international sensation.''

Noting that some Czech radio stations led their newscasts with the item, it said the story was received as ''an extremely alarming sign which confirms that there exist imperial aspirations in Russia.''

Soon afterward, the news agency apologized on its wire for any misunderstanding.

Boris Zaitsev, the day filing editor, told the Associated Press that ''the Czechs and Bulgarians calmed down'' after receiving the explanation and apology.

Karel Borovka, Czech Foreign Ministry spokesman, told ITAR-Tass that while he understood the humor, such ''jokes'' might give the shakes to those who forget it's ''All Fools' Day.''

Perhaps the shock was lessened by the fact it came just weeks after Russia's Communist-led lower house of parliament resolved to restore the Soviet Union. Radio officials in Prague and Sofia said they received no calls from listeners before the joke was revealed.