The last Soviet memorial in Budapest, honoring Red Army troops who died while seizing the city from the Nazis, was defaced over the weekend by vandals with a can of red spray paint.

Police were alerted when a resident telephoned to say someone had scaled a protective fence surrounding the 16-foot-tall obelisk and scrawled Prime Minister Gyurcsany’s last name on it, spokesman Oszkar Sass said by phone yesterday.

The monument, adorned with a hammer-and-sickle and Soviet star, infuriates many Hungarians who say it honors invaders who brought 40 years of communist oppression. Rioters attacked the memorial last September on the first night of anti-government protests demanding Mr. Gyurcsany’s resignation. A petition drive calling for removal of the statue was launched earlier this year.

“We have no idea who did it,” Mr. Sass said. “We’re going to investigate the scene and see what we come up with.”