Thousands of people demonstrated in the streets today while Argentina’s Senate debated the merits of a bill allowing same-sex marriage.

The bill was recently passed by the lower house by 125 votes to 109. If it passes the Senate, it will go to President Cristina Fernandez de Kirchner, who supports the legislation.

If passed into law, the bill will give gay couples in the country equal marriage rights, including the right to adopt children.

Religious groups led today’s protest outside Congress, while a smaller rally of pro-gay marriage supporters demonstrated in another part of the city.

There have been reports that faith leaders have lobbied senators to reject the bill, although one senator, Miguel Angel Pichetto, told the state-run Telam news agency that he had not been pressured.

“There is some pressure in some provinces where the church plays a prominent role, but such is democracy,” he said.

This week, Argentina’s highest-ranking Catholic prelate warned that the bill is the work of the devil.

Cardinal Jorge Bergoglio called on priests in Buenos Aires, where he is archbishop, to protest against it.

In a letter to the monasteries of the city, he wrote: “Let’s not be naive, we’re not talking about a simple political battle; it is a destructive pretension against the plan of God.

“We are not talking about a mere bill, but rather a machination of the Father of Lies that seeks to confuse and deceive the children of God.”

Ninety-one per cent of Argentinian citizens describe themselves as Catholic, and if passed, the bill will make Argentina the first Latin American country to approve gay marriage.

Currently, only a few areas of Argentina recognise civil unions between same-sex couples: Buenos Aires itself, the province of Río Negro in Patagonia, and the city of Villa Carlos Paz in Córdoba province.

Since the 2002 decision to allow civil unions, Buenos Aires has become one of the hotspots on the international gay-friendly tourist circuit.