TUNIS (Reuters) - Thousands of Tunisian lawyers went on strike on Friday to protest at new taxes and tighter fiscal controls on their profession, extending a series of demonstrations against austerity measures in the 2017 budget.

Several hundred attorneys held a symbolic protest outside the palace of justice in downtown Tunis where, dressed in their court gowns, they chanted "Down down with the shameful law" and "We are united in the fight".

Attorneys are the latest group to join protests against Prime Minister Youssef Chahed's measures to cut the budget deficit and increase government revenues by levying new taxes and freezing public wage increases.

Under pressure from international lenders for reforms to cut spending, spur growth and create jobs, Chahed has proposed a broad package of initiatives, but he must also manage social unrest that his measures may trigger.

Thousands of lawyers stopped working for a one-day "Day of Rage" and threatened more such strikes if Chahed did not remove the proposed tax on law practices that was included in the 2017 budget approved by the cabinet last week.

"Lawyers are being exposed to a financial massacre... We reject this law strongly," Ameur Mehrzi, the Tunisian Bar president, told reporters at the Tunis protest.

Under the proposal all lawyers will pay a tax ranging from $8 to $25 on each file they present to the court.

Tunisia has been praised for its democratic progress since ousting Zine El-Abidine Ben Ali in a 2011 uprising. But many Tunisians are worried about more taxes and austerity measures adding to a lack of economic development since the revolution.

Chahed said last month that Tunisia is going through hard times and all citizens must share sacrifices to save the country's economy and cut back on spending.

The powerful UGTT labor union threatened on Thursday to hold a general strike and called protests against the government's plans to freeze public wage increases, which it warned could trigger protests.

The UTICA industry and business employers' association, one of Tunisia's major economic lobbying groups, also rejected a proposed exceptional tax contribution on business as a way for the government to generate finances.

Tunisia expects to seek $2.78 billion in foreign loans next year - nearly double its 2016 external financing needs - to help cover a 2017 fiscal deficit expected to be 5.4 percent of GDP.

(Reporting By Tarek Amara; editing by Patrick Markey/Mark Heinrich)