By Naomi O'Leary

ROME (Reuters) - Italian hunting enthusiasts have killed 13 people and wounded 33 in shooting accidents since the season opened in September, increasing pressure to reform antiquated hunting laws.

The death toll swelled across the country this weekend when a 16-year old was killed by a friend while hunting, a pensioner was shot and wounded in his garden and a cyclist was hospitalized after being hit with grapeshot.

Hunting groups agree with environmentalists that the law - which allows hunters to roam on private land and discharge firearms within 150 meters (yards) of a house - should be changed. But the sides have become entrenched in a long-running stalemate over how.

Among those calling for an outright ban is Daniela Casprini, the head of the Association of Hunting Victims.

"The question is no longer about who is for and who is against hunting. This is to stop a true massacre," Casprini said on Monday.

Less than one in five Italians said they considered hunting to be an acceptable pastime in a survey by Italian research group Eurispes last year.

Pro-hunting groups point to a need to control populations of species like wild boar, which can cause damage to agriculture.

Yet the shooting of deer, rabbits and birds in the country's woodlands is the subject of a rift between a more ecologically sensitive younger generation and Italy's ageing hunters.

The number of hunters has declined steeply to about 700,000 from two million three decades ago, with most aged between 65 and 78 years, according to farming association Coldiretti.

The head of animal rights group Animalisti Italiani Onlus said the accidents proved that legislation to protect rare wildlife was ineffective.

"This explains why wolves, bears, hawks and other protected species are found killed by firearms," said Walter Caporale.

"They shoot because something moves."

(Reporting by Naomi O'Leary, editing by Paul Casciato)