Spain has said it will not hand over a leading Venezuelan opposition politician who escaped house arrest to help launch an abortive uprising, then sought refuge at a Spanish diplomatic compound and gave a press conference from its gates.

Leopoldo López claimed to have spoken to mid-ranking military officers in recent weeks, who told him they were privately committed to ousting the embattled president, Nicolás Maduro.

He also said on Friday that a military intervention in Venezuela would be “constitutional”, and he considered it an option for the opposition.

His comments, in an interview with the Spanish news agency EFE, came before the opposition leader, Juan Guaidó, announced a new wave of protests for Saturday. “We will continue in the streets” he said, calling for demonstrators to gather “in peace” at all the main military units across the country.

López, who is Guaidó’s political mentor and stood beside him as he tried to trigger a wave of military defections on Tuesday, is unlikely to join the protesters, as the supreme court has put out a warrant for his arrest.

The country has been in limbo since Guaidó posted a pre-dawn video on Twitter, calling for a popular and military uprising against the regime.

Thousands of protesters answered his call, but Venezuela’s military did not. Maduro remains in power and senior commanders and ministers have publicly pledged loyalty to him.

Demonstrations have continued around the country, however, with Venezuelan human rights groups saying five people have been killed and at least 200 injured. In a possible reflection of government concerns about fractured loyalties, and hawks in the US monitoring the situation, the administration has not moved against Guaidó.

Donald Trump has vowed to do everything short of “the ultimate” to resolve Venezuela’s crisis.

Senior US officials have alleged three senior Venezuelan officials were involved in plotting against Maduro, and in advanced talks with the opposition, when Guaidó was forced to bring forward the coup attempt, leading to its failure.

López, a former municipal mayor in Caracas, suggested the military’s loyalty was not yet assured. Having been detained in 2014 for leading protests against Maduro’s rule, he said five years surrounded by security forces had given him an insight.

“For more than three weeks, I had meetings in my home where I was held under house arrest,” López told reporters on the steps of the Spanish ambassador’s residence on Thursday.

“I met with commanders, I met with generals, I met with representatives of different units of the armed forces and the different branches of the police, and we agreed to put an end to the usurpation [by Maduro].

“And I can tell you that what began on April 30 is an irreversible process, and it’s irreversible because they themselves, the women and men of the armed forces, realised that they are not alone. They realised that they can work together, and they realised that together we – the people and the armed forces – can end the usurpation.”

The claim has been treated with scepticism, not least because López’s home was under close supervision by the feared intelligence agency.

Conversations with senior figures connected with the government also convinced him Maduro was surrounded by people who wanted him gone, López claimed.

Spain, a destination for thousands of Venezuelans fleeing economic collapse, has been a strong supporter of the opposition, recognising Guaidó as Venezuela’s legitimate president and urging Maduro to hold elections.

However, López’s brief foray back into the frontline of opposition politics – he has remained influential behind the scenes during his years under house arrest – may be curtailed by his new hosts.

Josep Borrell, the Spanish foreign minister, said the country would not allow the compound to be used as a centre for “political activities”, after the improvised press conference prompted a furious response from the Venezuelan ambassador to Spain.

“He is a guest and was received as a guest,” Borrell said. Under Spanish law, requests for asylum can only be made in Spain, so López is staying at the embassy until his next steps are clearer, the minister added.

López originally took refuge in the Chilean ambassador’s residence, then moved to the Spanish one. Chile’s foreign minister said it was a “personal decision”, since López and his wife are of Spanish descent.

His fellow opposition politician Freddy Guevara has been sheltered at the Chilean residence since 2017.