MADRID: Bomb disposal experts defused a fifth letter bomb on Thursday as Spain stepped up security to confront a spate of explosive devices sent to high-profile targets, including the prime minister and the Ukrainian ambassador in Madrid.

Early indications suggest that all five of the packages were sent from within Spain, the country’s Deputy Interior Minister told journalists.

Rafael Perez, the junior minister responsible for security, said the homemade devices were sent in brown packages containing a flammable powder and tripwire that would generate “sudden flames” rather than an explosion.

The packages were addressed to the heads of the institutions they were sent to.

Perez said one of the devices had detonated - injuring a security officer at the Ukrainian embassy in Madrid, three others were detonated by the security forces in controlled explosions and one had been kept intact for investigative purposes.

“It appears that they were all sent from within the country but we are basing this on early visual inspections without yet having an in-depth technical report,” he said.

Perez said it did not yet appear necessary to convene the security committee that would evaluate stepping up Spain’s terrorist threat level, which is already at the second-highest level following Islamist attacks around Europe in the past decade.

The Interior Ministry said in a statement that it had, however, ordered police to strengthen security around public buildings and particularly check postal deliveries carefully.

A source close to the investigation said that while the devices were homemade, “they were not something anyone could make”, and investigators were now seeking to trace their contents to their origin.

Spain’s High Court that specialises in terrorism has opened an investigation, a judicial source said.

Arms firms, EU satellite centre targeted

News of the letter bombs broke on Wednesday lunchtime after police said a security official at the Ukrainian embassy in Madrid had been slightly injured after opening a package.

Ambassador Serhii Pohoreltsev told the Ukrainian news site European Pravda that the suspicious package, addressed to him, was handed to the embassy’s Ukrainian commandant who took it outside to open.

“After opening the box and hearing a click, he tossed it and then heard the explosion…the commandant hurt his hands and received a concussion,” Pohoreltsev was quoted as saying.

“We have instructions from the ministry in Ukraine that given the situation we have to be prepared for any kind of incident… Russian activities outside the country,” Pohoreltsev told Spanish television station TVE.

Russia invaded Ukraine nine months ago in what it calls a “special military operation” that Kyiv and the West describe as an unprovoked, imperialist land grab.

After the incident, Ukrainian Foreign Minister Dmytro Kuleba ordered all of Kyiv’s embassies abroad to “urgently” strengthen security, a Ukrainian ministry spokesperson said.

The Twitter account of the Russian Embassy in Spain posted a statement on Thursday condemning “any threat or terrorist act” in relation to the five letter bombs, “particularly directed at a diplomatic mission”.

Another package was received on Wednesday night at the headquarters of Spanish weapons manufacturer Instalaza in Zaragoza, northeastern Spain, police said.

Instalaza manufactures the C90 rocket launcher that Spain has supplied to Ukraine.

Spanish security forces also found a device early on Thursday in an envelope mailed to a European Union satellite centre located at an air force base in Torrejon de Ardoz, near Madrid, the defence ministry said.

The satellite centre supports the EU’s common foreign and security policy by gathering information from space intelligence devices, according to its website, and was recently described by EU Foreign Policy Chief Josep Borrell as being part of “the eyes of Europe”.

On Thursday morning Spain’s Interior Ministry revealed that an “envelope with pyrotechnic material” addressed to Prime Minister Pedro Sanchez had been received on Nov. 24 and disarmed by his security team. The device was “similar” to packages discovered this week, it said.

A fifth device was received at Spain’s Defence Ministry on Thursday morning and defused by specialist police officers, a defence ministry spokesperson told Reuters.