MADRID (AP) -- Police in Spain detonated a suspicious parcel discovered at the U.S. Embassy in Madrid, Spanish officials said Thursday, a day after a similar package sent to the Ukrainian Embassy ignited upon opening and injured an employee.
"We can confirm a suspicious package was received at the U.S. Embassy in Madrid, and are aware of reports of other packages sent to other locations throughout Spain," the American embassy said in a response to an Associated Press inquiry.
"We are grateful to Spanish law enforcement for their assistance with this matter," it added.
Spain's police said the detonated parcel "contained substances similar to those used in pyrotechnics."
The action followed police reporting that multiple explosive parcels were sent in Spain over the past two days. Police said they were delivered to Spain's Defense Ministry, a European Union satellite center located at the Torrejón de Ardoz air base outside Madrid and to an arms factory in northeastern Spain that makes grenades sent to Ukraine.
Authorities said a bomb squad also destroyed an explosive device that was dispatched by regular post to Spanish Prime Minister Pedro Sánchez on Nov. 24.
Spain's interior ministry, which is charge of the country's police forces, said the envelope intercepted at the American embassy's security screening point was "of similar characteristics as the previous ones." It was then detonated by authorities after a wide area was cordoned off by Spanish police around the embassy in the center of Spain's capital.
Spanish authorities have yet to determine who was responsible for the letters or link them to the war in Ukraine.
The Russian Embassy in Madrid on Thursday condemned the letter bombs, saying in a tweet that "any threat or terrorist attack, especially those directed at diplomatic missions, are totally condemnable."
The package sent to the Ukrainian Embassy was addressed to the country's ambassador to Spain, Serhii Pohoreltsev. The employee handling it was slightly injured when it burst into flames.
In an interview Wednesday following the blast, ambassador Pohoreltsev told European Pravda, a news website linked to the Ukrainska Pravda newspaper, that the explosion could have been more serious but for the professional behavior of the injured employee.
He said the parcel looked suspicious to the secretary of the ambassador because there was no return address and it did not look like a typical diplomatic post.
"The package contained a box, which caused suspicion to the commandant and he decided to take it outside -- with no one in the vicinity -- and open it. After opening the box and hearing a click that followed, he tossed it and then heard the explosion," said the ambassador.
The embassy employee was treated for light wounds on his hand and later returned to work.
Spain's National Court is investigating the incident as a terrorist act.
Ukrainian Foreign Minister Dmytro Kuleba ordered stepped-up security at all of Ukraine's foreign embassies abroad and asked his Spanish counterpart for a fast investigation.
Two further Ukrainian embassies received threatening letters Wednesday, Kuleba said on the sidelines of a high-level security meeting in Lodz, Poland, on Thursday.
Kuleba added, without giving details, that "other disturbing events took place" Wednesday, involving "the sending of very concrete threats to Ukrainian embassies."
He declined to specify the embassies in question.
An initial assessment indicated the first five packages were likely sent from within Spain, Secretary of State for Security Rafael Pérez said. Police said all but one of the letter bombs were disposed of.
Pérez said the one intact explosive device was from the air base and that it and its packaging would be part of the investigation.
Officials said that package was sent to the director of the European Union Satellite Center. The center, known as SatCen, is an EU geospatial intelligence body, and and its missions include monitoring Ukraine.
"The Spanish authorities were immediately alerted, they safely disabled the parcel and they have started their investigations," said Nabila Massrali, EU spokesperson for Foreign Affairs and Security Policy.
"Nobody has been injured and the situation is under control."
The Defense Ministry package was addressed to Defense Minister Margarita Robles, Pérez said. Spain has contributed both military and humanitarian aid to Ukraine since the start of the Russian invasion.
Robles was visiting Ukraine on Thursday to support its defense effort with another aid bundle. Authorities did not provide details about the aid, saying they did not want to give away sensitive information to Russia's forces.
Robles said the disturbing discoveries of recent days would have no effect on Spain's full backing of Ukraine.
"The police are investigating these packages, but let one thing be perfectly clear," she said in Spanish. "None of these packages or any other violent act will change the clear and firm support that Spain and other NATO and EU countries have for Ukraine."
The arms factory targeted is located in the northeastern city of Zaragoza. The parcel was addressed to the factory's director.
A government official in Zaragoza said that both the arms factory and Ukrainian Embassy packages had the same email address listed as the sender. No further details were given.
The sending of small explosive devices in postal parcels is not uncommon in many countries. They were a common occurrence for many years in Spain, especially during the most active years of the now-defunct armed Basque group ETA.
Pérez said security was increased at public buildings following the discovery of the package sent to Spain's prime minister. The move now has been extended to embassies, which already had extra security measures in place after the start of the Russian invasion of Ukraine in February.