The head of Georgia's influential Orthodox Church called Thursday on the authorities to ban a gay rights rally set to be held in the deeply religious country.

The call came a day before gay rights activists were to stage a brief demonstration in central Tbilisi to mark the International Day against Homophobia.

"Any religious and scientific teaching -- except for modern pseudo-science -- considers homosexuality to be an anomaly and illness," Patriarch Ilia II wrote in an open letter to Tbilisi's mayor.

"The authorities should annul permission given to homosexuals for the demonstration," he added.

Ultra-conservative Orthodox believers have said they will hold a simultaneous counter-demonstration and have threatened to disrupt the gay rally.

A year ago a similar gay rally -- the first of its kind to be held in Georgia -- was violently broken up by a group of Orthodox priests and their supporters shouting abuse and aiming punches at rights activists.

In a statement released on Thursday the country's billionaire Prime Minister Bidzina Ivanishvili pledged that police would protect the gay rally and said the government was committed to defending the rights of minorities.

Their "rights are human rights and the government of Georgia is committed to upholding the rights of all of its citizens," Ivanishvili said in the statement.

In safety guidelines issued ahead of the rally, gay rights group Identity said there was "a reasonable expectation that the demonstration will end peacefully, without confrontations."

Homosexuality is still highly stigmatised in Georgia, a deeply socially conservative ex-Soviet state in the Caucasus where the Orthodox Church retains immense clout.