Belgrade, Serbia-Montenegro ? Snipers assassinated Serbia’s prime minister as he walked into government headquarters at midday Wednesday, silencing a pro-Western leader who helped topple Slobodan Milosevic and declared war on organized crime.

The slaying of Zoran Djindjic in downtown Belgrade prompted the government to impose a nationwide state of emergency amid fears the Balkan nation could plunge into a violent power struggle. The Cabinet declared three days of mourning.

It was the first assassination of a European head of government since Swedish Prime Minister Olof Palme was gunned down in Stockholm in 1986.

Djindjic, 50, died in a hospital after being shot in the abdomen and back, said Nebojsa Covic, a deputy prime minister. One of Djindjic’s bodyguards was wounded, police sources said.

Police sources told The Associated Press two snipers firing from a building across from government headquarters shot Djindjic as he slowly left his car on crutches after suffering a soccer injury to his foot. A high-powered bullet left a dent on Djindjic’s armored car.

Two suspects were arrested, witnesses said. But police, unsure they were the gunmen, launched a nationwide search, setting up roadblocks in Belgrade and halting bus, rail and plane traffic from the capital. Witnesses said suspects fled in a red car.

The government blamed Milorad Lukovic, a warlord loyal to Milosevic, and several other top underworld figures for organizing the killing.

“Their aim was to trigger fear and chaos in the country,” a government statement said.

The U.S. Embassy urged Americans in Serbia to exercise caution after the assassination, which occurred three blocks from the embassy.

A woman lights a candle for slain Serbian prime minister Zoran Djindjic in front of Serbia's government building in Belgrade. Djindjic was assassinated Wednesday.

Citing danger to “constitutional order,” acting President Natasa Micic imposed a state of emergency, giving the military the same powers as police to investigate and detain suspects without a warrant.

“The state will use all means at its disposal until the perpetrators of this crime … are brought to justice,” Micic said.

Under the constitution, Micic must nominate a successor to be approved by the Serbian parliament. Funeral plans for Djindjic were not immediately announced.

Djindjic had many enemies because of his pro-reformist and Western stands.

He was despised by some for arranging the extradition of Milosevic to the U.N. war crimes tribunal in The Hague, Netherlands, in 2001, and for urging more arrests of war crimes suspects.

He also was targeted by Serbian crime bosses and warlords who were allied with the former Yugoslav president.

When Milosevic was toppled in October 2000 in a popular revolt, Djindjic admitted luring key mob figures into changing sides. But later, he turned against them, declaring an open war on the rampant smuggling of contraband goods and drugs.

Drive-by shootings, explosions and mafia-style shootouts have been commonplace in Serbia, which still is recovering from Milosevic’s ruinous 13-year rule.

“Dark forces who have mushroomed in the country since the 1990s are trying to turn back the clock,” said Dobrivoje Radovanovic, an independent crime expert.