Spains foreign minister on Thursday compared the death of a Venezuelan activist in government custody with cases that took place during his countrys fascist dictatorship when prisoners being interrogated suddenly "jumped out of the window".

Fernando Alban, a Caracas city council member accused of taking part in a failed drone attack on President Nicolas Maduro, died on Monday while in pretrial detention in an incident that has sparked international outrage.

Authorities say the 52-year-old committed suicide by jumping out of a 10th-floor window of the state intelligence service headquarters, but his supporters counter that he was murdered.

"It brings to memory events during the last years of (dictator Francisco) Franco's regime when prisoners who were being interrogated in police departments also jumped out of the window," Foreign Minister Josep Borrel told reporters.

One case that shook Spain during the 1939-1975 dictatorship was that of leftwing student Enrique Ruano, whom authorities said committed suicide by throwing himself from the seventh floor while in police custody.

His family has always maintained he was murdered.

Borrell stressed that such incidents in Spain towards the end of Franco's regime could not be compared to what is happening in Venezuela.

But he added the Venezuelan government would have to "give explanations, just like any country would have to if this kind of event took place".

"People don't jump out of windows from a tenth floor, something must have happened for this to take place," he said.

The United Nations, European Union and several countries -- including Spain -- have asked for an independent investigation into what happened in Caracas.

Borrell was speaking after meeting his Brazilian counterpart Aloysio Nunes in Madrid.

Both said they would not join a call by multiple countries for the International Criminal Court (ICC) to investigate Maduro's government for crimes against humanity.

The request was made at the end of September by Argentina, Canada, Chile, Colombia, Paraguay and Peru, and is supported by France.

Both ministers said the ICC had already started its own probe and the legal basis for accusing the Venezuelan government of crimes against humanity was "not very clear".

Borrell added it could also harm countries' "ability to maintain and establish political dialogue" to ease the crisis in Venezuela, where an economic collapse has seen hundreds of thousands flee the country.