With the world's most powerful leaders gathering in this city just three months after a devastating earthquake, Italian security officials have prepared an emergency evacuation plan to airlift the leaders to safety in case of another powerful tremor.

The evacuation plan is part of massive security measures to protect the leaders of the Group of Eight industrialized nations meeting in L'Aquila starting Wednesday. Italy is deploying thousands of policemen as it seeks to avoid the violence that marred the last G-8 summit held in this country, when one protester was killed and more than 200 were injured in Genoa in 2001.

The April 6 earthquake leveled entire blocks in L'Aquila and the surrounding Abruzzo region, driving some 54,000 from their homes and killing 296 people. Premier Silvio Berlusconi decided to move the summit from a posh Sardinian island to L'Aquila in a show of support to the stricken population.

But since the quake, daily aftershocks have hit the area, causing further distress to survivors in tents scattered across the area — and serving as a powerful reminder of the potential dangers facing the world's leaders. On Friday, a 4.1 magnitude tremor hit just about kilometer (mile) away from the police barracks that will host U.S. President Barack Obama and the other leaders.

"I think that there will be some little aftershocks: It's not like the Earth stands still because Obama gets here and then starts moving again after the G-8 ends," Enzo Boschi, the president of Italy's National Institute of Geophysics and Vulcanology, said this weekend after the latest shocks.

But he stressed that the police barracks serving as the summit venue is solidly shockproof and runs no risk.

Guido Bertolaso, the Civil Protection czar who is in charge of the G-8's organization and the relief operation in the quake zone, also played down any risks. He noted that the police complex had resisted the April 6 temblor and said that for it to be endangered "there would have to be an earthquake of a strength that has never been seen in L'Aquila."

Still, officials are taking no chances.

"An evacuation plan is ready and naturally we are ready with alternative ... accommodation in other places," Italy's national police chief Antonio Manganelli said Monday. A Berlusconi aide, speaking on customary condition of anonymity, said that "a series of possible emergencies have been studied, and in light of this we feel we can guarantee the maximum security."

Officials have not publicly discussed details of the plan. But according to Italian newspapers, the leaders would be transferred to tents set up in the police barracks and then transferred by helicopters. The delegations accompanying them would leave the area by car, according to the newspaper La Repubblica, and a backup plan even envisages the transfer to Rome, at another police barracks — even though this is seen as a highly complicated move logistically.

The transfer to the Italian capital would take place in case of a tremor of around magnitude 4.5, according to Italian newspaper Corriere della Sera and other reports. Based on what happened in the aftermath of the April quake, officials estimate that there is a 30 percent chance that shocks with a magnitude higher than 4 percent will hit the area in the span of a week, said Sonia Topazio of the Institute of Geophysics and Vulcanology.

The world leaders arrive in L'Aquila, a Medieval city in the Apennine mountains, shortly before the opening of the summit at lunch time Wednesday.

The police complex hosting the talks and housing the leaders for three days and two nights already served as the headquarters of relief efforts in the aftermath of the quake and was the site of the funeral of the quake victims.

The area, in the Coppito district just outside L'Aquila, is cordoned off for the whole week and guarded by thousands of policemen. Sharpshooters will guard the barracks' perimeter.

Security officials have not disclosed details of their plan, but the number of police forces deployed during the summit is estimated at around 15,000. They will be both in L'Aquila and Rome, where delegations will arrive by plane before transferring to L'Aquila and where some of the anti-globalization demonstrations are planned.

Roads in and around L'Aquila will be closed to traffic or guarded by roadblocks, while many offices, restaurants and shops were shutting down.

Italy is also reactivating border controls with European countries that are part of the Schengen agreement, which allows free travel among them. The agreement has been suspended from June 28 until July 15, aviation officials said.

The measure is mainly aimed at keeping track of any protesters coming from abroad. Some of the demonstrations will be held in Rome, but at least one march has been scheduled in the Abruzzo on Friday, the day the summit ends. Road blocks and massive police deployment will make it hard for protesters to come anywhere near the center of town.

On Tuesday, police in L'Aquila seized a baseball bat and metal sticks from the car of five French protesters during a routine check in the area, said local Carabinieri official Amedeo Specchia. The five were not arrested.

In Rome, anti-G-8 protesters clashed with police at an impromptu demonstration near a university and 36 people were arrested, police in the Italian capital said.

While the anti-globalization movement has lost momentum in the past years, the memory of massive anti G-8 demonstrations and violence has not faded.

In 2001, some 100,000 protesters descended on Genoa during the G-8 summit to champion a variety of causes, from debt relief to the environment. A small group turned violent, torching cars, smashing windows of stores and banks and hurling paving stones and bottles at police, who used tear gas and clubs to battle back. Police faced widespread accusations of brutality and incompetence for their handling of street protests. Scores of foreigners were among those detained.

The violence that marred the summit overshadowed the leaders' talks and proved an embarrassment for Berlusconi, who was also in power then and had been following the summit's organization in detail, down to the flower arrangements. A 23-year-old protester was shot dead by a Carabinieri policeman. The protester was rushing at a police jeep, apparently about to hurl a fire extinguisher at the police inside the vehicle when he was shot.