SAO PAULO/RIO DE JANEIRO, April 28 (Reuters) - Brazilian unions called nationwide strikes on Friday to protest President Michel Temer's efforts to reduce social security benefits and weaken labor laws, with disruption expected to road and rail transport, factories and schools.
Many workers were expected to heed the strike call, due in part to anger about reforms that will force many Brazilians to work for years longer before drawing a pension, but also because the strike will extend a holiday weekend ahead of Labor Day on Monday.
If successful, the protest would mark Brazil's first general strike in more than two decades.
In Brasilia, the capital, authorities boarded up windows of government buildings on Thursday amid fears that protests could result in violent clashes between demonstrators and police.
Demonstrations were scheduled in other major cities across the Latin American nation of more than 200 million people.
"It is going to be the biggest strike in the history of Brazil," said Paulo Pereira da Silva, the president of trade union group Forca Sindical.
Violent protests have occurred repeatedly during the past four years amid political turmoil, Brazil's worst recession on record, and unprecedented corruption investigations that revealed stunning levels of systematic graft among politicians.
Nearly a third of Temer's cabinet and key congressional allies came under investigation in the scandal this month, worsening his dismal approval ratings since taking office last year after the impeachment of ex-President Dilma Rousseff.
Rousseff's Workers Party grew out of the labor movement, and her allies have called her removal for breaking budget rules an illegitimate "coup," contributing to political polarization in Brazil and hardline union resistance to Temer's agenda.
Vagner Freitas, the national president of the Central Workers Union (CUT), Brazil's biggest labor confederation, said the government's reforms "leave no room to negotiate."
"Temer does not even want to negotiate, he just wants to meet the demands of the businessmen who financed the 'coup' precisely to end social security and legalize the exploitation of workers," Freitas said in a statement.
A spokesman for Temer rejected the union criticism, saying the government was working to undo the economic damage wrought under the previous Workers Party government, which had the backing of the CUT.
"The inheritance of that was 13 million unemployed. The government is carrying out reforms to change this situation, to create jobs and economic growth," said spokesman Marcio de Freitas. (Reporting by Brad Brooks in Sao Paulo and Pedro Fonseca in Rio de Janiero; Additional reporting by Anthony Boadle in Brasilia; Editing by Daniel Flynn and Leslie Adler)