Caracas (AFP) - Venezuelan opposition leader Juan Guaido on Saturday urged his supporters to reject fear and maintain nationwide protests against President Nicolas Maduro, who has been ratcheting up pressure on the lawmaker since a failed military uprising.

Some 1,500 to 2,000 people filled a square in an opposition-friendly part of eastern Caracas to hear Guaido, but that was far fewer than the several thousands who took part in earlier protests.

Anti-Maduro rallies in other cities also appeared to be smaller than in previous weeks, based on photos and videos posted on social media.

The smaller turnouts were seen as a sign of possibly waning interest -- or simply exhaustion -- after months of protests climaxed in a failed uprising April 30, leaving six people dead.

"We are at a historic moment," Guaido told the crowd in Caracas, urging them not to give up their fight. "Either we are prisoners of fear, hopelessness and inaction... or else we continue to fill the streets with hope, with power, with confidence."

Melquiades Rosales, a 42-year-old Guaido supporter at the Caracas rally, said he had expected a bigger turnout but added, "We may all be afraid of repression, but we cannot stay home."

Guaido, who is recognized by more than 50 countries as Venezuela's interim president, has faced a series of setbacks.

His deputy Edgar Zambrano was arrested by Maduro's SEBIN intelligence service and stands accused of "treason, conspiracy and civil rebellion," the Supreme Court said. Three other lawmakers have sought refuge in diplomatic facilities in Caracas, while one fled to neighboring Colombia.

Guaido issued a call on Twitter late Friday for people to turn out Saturday and "take to the streets for our National Assembly... (and) for our brave lawmakers who are giving everything they have and for an entire nation that remains mobilized to win its freedom."

Against a backdrop of spiraling economic crisis and grave shortages of food and medicine, Guaido and Maduro have been battling each other since early this year when the 35-year-old lawmaker, the head of the National Assembly, declared himself acting president.

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Guaido, who says Maduro rigged his own re-election last year, has repeatedly led street demonstrations and called on the military to turn their backs on Maduro, who retains key support from China and Russia.

- CIA 'mole' -

So far, the armed forces have remained in Maduro's corner, except for about 30 military personnel who heeded Guaido's call for an uprising last month. The attempt to unseat Maduro, the political heir of the late Hugo Chavez, proved abortive.

On Friday, Maduro accused his sacked intelligence chief of being a CIA "mole" and the architect of the failed military uprising.

"He was captured by the CIA a year ago and was working as a traitor, mole and infiltrator," Maduro said of Cristopher Figuera, who has defected to the opposition.

Figuera and 55 other officers have been expelled from the Venezuelan armed forces.

Zambrano -- who is being held in a military prison -- is one of 10 opposition lawmakers charged with treason for participating in the April 30 movement.

One of the others, Luis Florido, announced in a video on Friday that he had fled to neighboring Colombia.

Three others -- Richard Blanco, Mariela Magallanes and Americo De Grazia -- have sought refuge in the residences of the Argentine and Italian ambassadors in Caracas.

Guaido said on Thursday the arrests were part of a bid by Maduro to dismantle the National Assembly legislature, Venezuela's sole opposition-controlled institution but one which had already been rendered powerless by the pro-Maduro Supreme Court.

"The National Assembly was elected by popular vote. (The government) cannot dissolve it by persecuting lawmakers," said one protester in Caracas, Alexander Mendoza.

- Uncertainty -

The United States and the European Union have condemned the Maduro government's actions against opposition lawmakers.

On Friday, Washington imposed sanctions on two shipping companies for delivering Venezuelan oil to ally Cuba.

US President Donald Trump has said all options remain on the table, implying the possibility of military action.

But in an interview with Portuguese television aired Saturday, Guaido said a foreign military intervention could happen only as a "last option."

He told the crowd in Caracas, nonetheless, that he had asked his representative in Washington, Carlos Vecchio, to contact Admiral Craig Faller, commander of the US Southern Command, and "establish direct relations on matters of cooperation."

Venezuela's navy on Friday denounced what it said was an incursion by a US Coast Guard vessel into its exclusive economic zone.

"This is not a request (and) I am not asking for a favor," Defense Minister Vladimir Padrino said bluntly in a speech Saturday. "We demand that the American military authorities respect waters in our jurisdiction."