A priest has carried out an aerial exorcism over the seaside town of Castellammare di Stabia in Italy to cast away demons believed to be plaguing the area following a series of thefts in churches and crosses being turned upside down.

Following a request of a local prayer group, a priest used a helicopter in performing a minor exorcism over the whole town, the Catholic News Agency reported.

"If Satan exists, he has taken control of Castellammare di Stabia," the group said in a statement. "There was nothing left but to try the exorcist."

The town has long been infested with violence from organised crime, but what made locals believe that something more sinister was at work were the series of thefts in churches, desecration of graves, statues of Mother Mary being tossed over cliffs, and crosses being turned upside down.

Locals hope that the exorcism will revive life in the town, which has been in moral and economic decline.

The exorcism was performed on July 9 but was announced by the group only one week later.

Although the use of a helicopter was unique in this case, exorcism over an entire country has already been carried out over Mexico in May.

The "Exorcism Magno" was performed quietly in the cathedral of San Luis Potosí by Cardinal Juan Sandoval Íñiguez, the archbishop emeritus of Guadalajara, Mexico, following the high levels of violence, drug cartels, and abortion in the country.

Spanish demonologist and exorcist Father José Antonio Fortea, who attended the exorcism, warned: "To the extent there is more witchcraft and Satanism going on in a country, to that extent there will be more extraordinary manifestations of those powers of darkness."

He also said that a single ceremony will not change Mexico overnight.

"It would be a big mistake to think that by performing a full scale exorcism of the country everything would automatically change right away."

But he also said that "if with the power we've received from Christ we expel the demons from a country, this will certainly have positive repercussions, because we'll make a great number of the tempters flee, even if this exorcism is partial."