Activist Leopoldo López took refuge at the Spanish ambassador's home in the Venezuelan capital this week and spoke to reporters Thursday, urging people to support opposition leader Juan Guaidó.
Venezuela's ambassador in Madrid told Radio Nacional de España that permitting López to urge Venezuelans to back the uprising is "inappropriate."
"It's extraordinary for (López) to use the ambassador's residence as an operational base to abet a military uprising," said Ambassador Mario Isea, according to private Spanish news agency Europa Press.
During a visit to the Lebanese capital of Beirut, Spain's acting foreign minister reiterated that López is only a guest at the Spanish embassy in Caracas and cannot utilize the building as a headquarters for opposition activity.
"He is a guest and was received as a guest," Minister Josep Borrell said. "We can't permit that the Spanish embassy be the center of political activities in Venezuela."
López went to the Spanish embassy days after breaking house arrest to join an attempted military revolt against Maduro. He was detained in 2014 for leading protests against Maduro's rule, but was freed this week.
Venezuela's top court has ordered López's arrest, but Spain has refused to hand him over.
Spain says if López wants to request political asylum he can only do so inside Spain.
The South American nation is embroiled in a months-long power struggle between Guaidó and Maduro, whose socialist government is reviled across much of the country amid a deepening economic and humanitarian crisis.
Human rights groups say protests this week have left at least five people dead. Fifteen-year-old Yonder Villasmil was killed during a demonstration over persistent blackouts in the northwestern state of Mérida on Thursday night, according to the Venezuelan Observatory of Social Conflict. The organization reports that over 200 people have been injured in clashes between protesters and state security forces.
On Friday the Lima Group of a dozen nations backing Guaidó said they would ask the "International Contact Group" to hold a joint meeting to discuss ways to converge their efforts in finding a return to democracy for Venezuela.
The "International Contact Group" of several European and Latin American nations is pushing both sides to reach an agreement on holding new elections.