Thousands in Portugal demonstrated against salary and public sector cuts as parliament approved the 2014 budget under the country's international bailout deal.

Just before the vote on the first reading of the budget -- the definitive version will be voted on November 26 -- a dozen protesters from the gallery inside parliament interrupted Deputy Prime Minister Paulo Portas's speech with demands to resign before police forced them out.

After nearly three years of belt-tightening, the budget aims to save a further 3.9 billion euros ($5.3 billion), partly through cutting public sector salaries and pensions.

A coalition led by the conservative ruling party holds a comfortable majority in parliament and it was able to approve the budget plan despite the opposition MPs voting against.

Earlier in the day, protesters in Lisbon waved signs calling for the government to stand down and messages such as "The budget is a theft" and "Get lost, troika."

Troika refers to the three international bodies that agreed Portugal's 78 billion euro ($108 billion) rescue deal in 2011 -- the European Union, European Central Bank and International Monetary Fund.

In return for the bailout money to prevent the indebted country from financial collapse, the troika demanded economic reforms to get Portugal's public deficit down to four percent of output by 2014.

"The hour has come for the government to go," demonstrators shouted at the rally organised by Portugal's main union (CGPT), which said the budget "destroys jobs, steals salaries and pensions, cuts health, welfare and education."

"They are all crooks and thieves," said retired public sector worker Maria Hernani, shaking her fist at the parliament building.

"Everything in this budget is scandalous: the salary and retirement cuts, but also in health and education," said Maria Joao Faria, a psychologist.

"It's like we're living through the Robin Hood folktale and the troika is the Sheriff of Nottingham," added Nuno Amaro, who works in the automobile industry.

But despite the protests, the government so far has shown no sign of changing course in its reforms and is hoping to complete the bailout programme by next June.

"I will not hide the fact that the budget is difficult," said Portugal's Prime Minister Pedro Passos Coelho before the vote. "All members of the government are aware of the sacrifices the Portuguese people are being asked to make."

Labour unions have called a strike by public sector workers for November 8, among various other demonstrations and stoppages including a police protest on November 21.

"Nobody believes this budget will get Portugal out of the crisis. It is not a state budget, it is a cuts plan to impoverish the country," said Antonio Jose Seguro, leader of the opposition Socialist Party.