Debt-mired Ireland is facing a revolt over its new property tax.

The government said less than half of the country's 1.6 million households paid the charge by Saturday's deadline to avoid penalties. And about 5,000 marched in protest against the annual conference of Prime Minister Enda Kenny's Fine Gael party.

Emotions ran raw as police backed by officers on horseback stopped demonstrators from entering the Dublin Convention Centre. Many protesters booed and heckled passers-by who were wearing Fine Gael conference passes, some screaming vulgar insults in their faces.

Protesters jostled with police as they tried to block the way of Fine Gael activists using a back entrance. One man mistakenly identified as the government minister responsible for collecting the tax had to be rescued by police from an angry scrum.

Kenny said his government had no choice, but to impose the new charge as part of the nation's efforts to emerge from an international bailout. Ireland already has endured five emergency budgets in four years and expects to face at least four more years of austerity.

"The household charge is the law of the land," said Kenny, who noted that people were paying the tax over the Internet at a rate of 5,000 an hour Saturday.

Council offices also were ordered to remain open Saturday to help taxpayers meet the deadline. But the last-minute push wasn't nearly enough as the agency handling tax collection said just 735,000 households had paid by Saturday night.

The charge this year is a flat-fee (EURO)100 ($130) per dwelling, but is expected to rise dramatically next year once Ireland starts to vary the charge based on a property's estimated value. Anti-tax campaigners have urged the public to ignore the tax demand, arguing that the government doesn't have the power to collect it.

Ireland imposed the charge as part of its ongoing negotiations with the European Union, European Central Bank and International Monetary Fund, which in 2010 provided Ireland a (EURO)67.5 billion ($90 billion) credit line to pay its bills through 2013.

The donors require Ireland as part of the deal to reduce its annual deficits by slashing spending and raising taxes, and specified Ireland's lack of property-based tax as an obvious target.

In 2011, Ireland posted a deficit of 10 percent of gross domestic product, hopes to lower that to 8.6 percent this year and reach the bailout accord goal of 3 percent by 2016.

Saturday's protesters traveled from every corner of the Republic of Ireland. Many carried placards bearing the slogans "No way, we won't pay!" and "Reject fear, austerity stops here!" One of the biggest banners suggested, "Tax the cheats that got us into this mess."

One man's handmade poster depicted Kenny and other politicians with the bodies of serpents and appealed to Ireland's patron saint: "Come back St. Patrick, it's still full of snakes."