ROME, June 3 (Xinhua) -- Saturday in the Italian capital began with a colorful display of unity and military might and ended with a major political celebration in one of Rome's most historic squares, as the country looked to put nearly three months of difficult and often acrimonious political negotiations behind it.

On Friday, Italy installed its first populist government under Prime Minister Giuseppe Conte, a law professor. The new government sparked fears across the European Union (EU) that Italy could put the future of the 19-nation euro zone into doubt, call for more flexibility on European budget rules, and otherwise seek to keep a distance from an increasingly interconnected continent.

Saturday, June 2, was Italy's Republic Day, an anniversary celebrated every year to commemorate the abolition of the Italian monarchy and the creation of the Italian Republic in 1946. This year's celebration included military marches, a parade and fighter planes speeding overhead and leaving green, white and red trails of smoke, the colors of the Italian flag.

Hours later, the Five-Star Movement (M5S), the largest vote getter in Italy's inconclusive March 4 general election and one of the two partners supporting the Conte government, held a massive and vocal rally in Rome's picturesque Piazza Bocca della Verita.

Between the two events, Jean-Claude Juncker, president of the European Commission, gave the new government he had previously criticized a qualified endorsement.

"I prefer to keep calm," Juncker said. "I will not interfere in domestic Italian affairs, even though I have been tempted to do so."

A day earlier, Juncker sparked fierce criticism in Italy by saying the country should stop blaming the EU for its problems, and that the country needed "more work, less corruption, more seriousness." Juncker later apologized for the remark.

On Saturday, Juncker, speaking on German television, was more cautious. "I do not want to feed the accusations spread by populists that we are sitting in Brussels and meddling with Italian affairs," he said. "They will sort it out."

If the M5S rally late Saturday is an indication, the new government will not be shy about standing up to the EU.

Luigi Di Maio, the M5S leader and minister of labor and deputy prime minister in the new government, took the stage at the event twice, and his speeches were peppered with warnings about keeping European powers "from interfering with country's finance ministries," and criticism of what he called the "tyranny of ratings agencies" that judge national economies and rate them based on risk.

Di Maio promised the new government in Italy was just a start, saying that "Change in Europe will start in this square."

Later, Di Maio introduced the eight government ministers who are the M5S members. Leaders of the nationalist League, the other partner in the new government, were not at the rally.

The crowd on hand grew as the evening went on, filling the large piazza and overflowing into nearby streets. Most on hand said they were optimistic about the prospects for the day-old government.

"You have to be hopeful," said Luca Albanese, a 51-year-old municipal worker. "The governments in the past didn't work and it's time we tried something new."

Anna Luisa Donati, 40, a homemaker, agreed. "I didn't vote for the Five-Star Movement but I have grown to like their message," she said. "I am tired of Italy taking commands from other countries. Now we will take our own path."