Thousands rallied in Lebanon's capital on Sunday against proposed tax hikes that the government has said are needed to avoid a $4bn budget deficit this year.

Protesters chanted "we will not pay" and blamed corrupt politicians as they gathered in central Beirut's Riad el-Solh square.

Addressing the crowd, Prime Minister Saad al-Hariri vowed to fight corruption.

"The road will be long ... and we will be by your side and will fight corruption," Hariri said. Protesters responded by shouting "thief" and hurling empty water bottles at the prime minister.

On Twitter, Hariri later urged the organisers of the protests to form a committee and "raise their demands and discuss them positively."

Police barricaded the entrance to the government headquarters and parliament building during Sunday's demonstration, which followed three days of smaller protests in Beirut.

Authorities are seeking to raise taxes to help pay for a deal on public sector pay increases, which is part of a wider effort led by Hariri to approve the country's first state budget in 12 years.

Lebanon faced years of political deadlock. A new government was formed in December of last year after more than two years without a president.

Legislators approved several tax hikes last week, the most prominent being a one percentage point increase in the sales tax.

Reporting from Beirut, Al Jazeera's Imtiaz Tyab said there was a lot of anger and frustration among protesters.

"When you consider the fact that many people in Lebanon really don't have high wages and you consider the fact many have some of the highest rates of personal debt as well, any kind of increase is going to be felt in the pocketbook," he said.

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In the coming weeks, parliament will vote on a number of other increases, all of which must be signed off by the president before taking effect.

In recent days, various civil society groups and some leading political parties have called for people to take to the streets in protest.

The Christian Kataeb party and the Progressive Socialist Party, led by Druze politician Walid Jumblatt, have staunchly opposed the new taxes. The Iranian-backed Shia Hezbollah movement has also voiced reservations about the increases.

Sunni leader Hariri became premier in October in a power-sharing deal that saw Michel Aoun, a staunch Hezbollah ally, elected president. Hariri, whose Saudi-backed coalition opposed Hezbollah for years, formed a unity cabinet that includes nearly all of Lebanon's main parties.

Aoun's election ended a 29-month presidential vacuum in a country that had been crippled by political gridlock for years.

"We had hopes for this new government, but unfortunately ... these politicians are still exploiting resources for their profit," said protester Mahmoud Fakih. "This is to refuse the taxes that are being imposed on poor people."

Signs and slogans accused parliament of theft and people chanted for politicians to step down. "Take your hands out of my pockets," one placard read.

Lebanon's parliament has extended its own mandate twice since 2013, a move that critics including the European Union have condemned as unconstitutional. Current lawmakers were elected in 2009 for what was meant to be four-year terms.

Anger at Lebanon's government has prompted repeated protests in central Beirut over the last two years, particularly in the summer of 2015, when politicians failed to agree on a solution to a rubbish disposal crisis.

Piles of rubbish festered in the streets, prompting massive protests that were unprecedented for having been mobilised independently of the big sectarian parties that dominate Lebanese politics.