* IMF warned Tunisia to keep public sector wages under control
* Strike is biggest in Tunisia in five years
* Economy was plunged into turmoil after 2011 uprising (Adds protests)
Nov 22 (Reuters) - About 650,000 public sector workers went on strike and thousands protested across Tunisia on Thursday over the government's refusal to raise wages amid threats from international lenders to stop financing Tunisia's tattered economy.
Schools, universities, municipalities and ministries were shut and hospitals were on emergency staffing only in the nationwide walkout organised by the UGTT union, the biggest strike action in Tunisia in five years.
Under pressure from the International Monetary Fund (IMF) and a deepening political crisis, Prime Minister Youssef Chahed is battling to push through unpopular economic reforms and reduce its budget deficit.
Tunisia's economy has been in turmoil since autocrat Zine al-Abidine Ben Ali was toppled in a 2011 uprising sparked by anger at unemployment and poverty.
Earlier this month the IMF warned Tunisia to keep its public sector wage bill - one of the world's highest in proportion to GDP, according to the IMF - under control to avoid severe debt problems.
Thousands of protesters gathered in front of parliament in the capital Tunis, calling for the government to resign and holding banners with slogans such as "Strike for dignity".
Thousands also took to the streets in cities including Sfax, Gabes, Sidi Bouzid and Kasserine. "The situation is very dangerous in light of growing inflation and low standard of living..the government will see soon a revolution of hungry and empty bellies," said Nourredine Taboubi, the head of the UGTT.
He said negotiations had failed because "the sovereign decision is not in the hands of the government, but of the IMF."
Tunisia struck a deal struck with the IMF in December 2016 for a loan programme worth around $2.8 billion to overhaul its ailing economy with steps to cut chronic deficits and trim bloated public services, but progress has been slow.
The government aims to cut the public sector wage bill to 12.5 percent of GDP in 2020 from the current 15.5 percent.
Prime Minister Youssef Chahed also faces a political crisis over his government's failure to solve Tunisia's economic woes.
"If Chahed was looking for populism or electoral interests, he would have signed the wage increase, but we want to know who will finance salaries increases" said the government spokesman Iyad Dahmani.
He added that the international lenders including the IMF had threatened to stop financing Tunisia in the absence of the reforms.
Public sector wages have doubled to about 16 billion dinars ($5.48 billion) in 2018 from 7.6 billion dinars in 2010, officials say.
($1 = 2.9195 Tunisian dinars)
(Reporting By Tarek Amara Editing by Raissa Kasolowsky)