Portuguese workers have protested the country's austerity measures by boarding dozens of buses and crisscrossing one of Lisbon's main bridges with their horns blaring.

Portugal's main labor group, the General Confederation of Portuguese Workers, organized Saturday's demonstration after authorities refused to allow the protesters to cross the 2.3-kilometer(1.4-mile)-long bridge on foot, citing safety concerns.

Trade unions are fighting pay and pension cuts and the scrapping of workers' rights — measures required by creditors in return for Portugal's 78-billion-euro ($100 billion) bailout in 2011.

In a similar protest in April, buses decked with flags and blowing their horns crossed the same bridge over the River Tagus in long lines before the workers aboard staged a demonstration in the city.

Unions are planning more strikes in November.