OVIEDO, Spain

Another letter bomb addressed to the EU Satellite Center in Madrid was discovered Thursday morning, just a day after a similar package exploded in the Ukrainian Embassy in Madrid.

According to the Interior Ministry, Spanish police also discovered a similar letter bomb addressed to Prime Minister Pedro Sanchez last Thursday.

In total, five letter bombs were sent to high-profile targets in Spain over the past week.

The first, addressed to Sanchez containing explosive material, was sent by ordinary mail and was deactivated by police.

The same day, the Interior Ministry told police to increase security around mail packages being sent to government offices, although it was not made public until a week later.

On Wednesday, a similar package addressed to the Ukrainian ambassador exploded in the Ukrainian Embassy in Madrid. One staffer suffered from minor injuries.

Later that night, the arms company Instalaza, which makes the C90 rocket-propelled grenade launchers that Spain sends to Ukraine, discovered another suspicious package. Staff reported it to the police and the bomb was deactivated.

Just a few hours later, early Thursday morning, security at the Torrejon Air Base in Madrid detected another suspected envelope directed to the European Union Satellite Center. After passing it through an X-ray machine, authorities saw it contained “a mechanism,” according to the interior minister.

Consequently, police were called to deactivate the explosive.

Also, another envelope was detected at the Defense Ministry in Madrid on Thursday, which was addressed to Defense Minister Margarita Robles, according to the sources who spoke to Spanish news agency EFE.

Although police are still investigating, Interior Minister Fernando Grande Marlaska said all four letter bombs, excluding the one directed to the Defense Ministry as it was known later, had "similar characteristics."

Rafael Perez, director general of the Civil Guard, later said that the five envelopes had "similar characteristics" and were sent from inside Spain, citing preliminary investigations.​​​​​​​

The Interior Ministry has increased security measures around consulates and other sensitive organizations, and the High Court is now investigating the cases.