Cordons and police are seen in front of the Colosseum in Rome, Italy, March 23, 2017. [Photo/Xinhua]

More than 30 EU leaders are expected to attend the ceremony in center of Rome, where the founding treaty was signed on March 25, 1957.

Police forces were on high alert, and their staff were increased to 5,000, while Italy's Civil Aviation Authority declared a full flight ban over Rome from 6 a.m. on Friday to 11 p.m. on Saturday.

At the same time, important venues in the capital would remain cordoned off, including parliament, government building, and presidential palace, while major tourist attractions would be closed.

A most restricted zone, namely the "Blue Area," was declared around the Capitoline Hill, where the celebrations will actually take place. It would be off-limits for all transport means and all citizens, but residents.

Some 40 checkpoints were set up at the main gates to the two zones, and about 100 additional surveillance cameras were installed across the capital, according to police.

The plan was imposed after an emergency meeting of the Counter-Terrorism Strategic Analysis Committee (CASA) was called on Thursday, also following London terror attack the previous day.

On request of Interior Ministry Marco Minniti, the CASA will meet in permanent session until after the EU summit.

On Saturday, the 27 leaders of EU member states and the representatives of EU institutions gather to mark the anniversary of the signing of the Treaty of Rome 60 years ago, which brought West Germany, France, Italy, the Netherlands, Belgium and Luxembourg as a common community, paving the way for the European Union.

The ceremony will be followed by a formal "Rome Declaration," and leaders are expected to outline Europe's future, especially after the forthcoming exit of Britain.