Recent months have seen a flurry of protests by drivers against the controversial smartphone-based taxi service amid claims Uber provides unfair competition by flouting rules and restrictions that regulate professional vehicles.
Uber launched in Lisbon a year ago but Antral, one of Portugal's main drivers' associations, obtained earlier this year a civil court ruling preventing the firm operating nationwide.
But the ruling was filed against Uber's US-based, rather than Europe-based, incarnation.
As some 400 drivers blocked thoroughfares including a main road to Lisbon airport and several hundred more drivers demonstrated in the northern city of Porto and Faro in the south, Antral slammed Uber for "illegally" continuing to operate, Lusa news agency reported.
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The Portuguese protests come in the wake of similar complaints elsewhere in Europe, the United States and India.
Uber resumed its Indian operations in January after last year being banned following a rape allegation against one of its drivers.
June saw angry scenes in Paris, resulting in rioting by taxi drivers and the arrest of two Uber executives.
The company responded by suspending its lower cost UberPOP service.
Unions representing taxis in Brussels have called a strike for September 16, with drivers from other European capitals also expected to participate.