MADRID: When a letter bomb was opened by a security guard at the Ukrainian embassy in Madrid on Wednesday, it was addressed to the ambassador of Ukraine. This incident prompted Kiev to increase security at its embassies.

According to Mercedes González, a representative of the central government in Madrid, the letter, which was delivered by regular mail, exploded at noon when guards opened it in the embassy garden.

Ukraine's ambassador to Spain, Serhiy Pohoreltsev, said the guard was released from hospital later on Wednesday and resumed his work.

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Pohoreltsev put the blame on Russia in an interview with Spain's state television: "We are well aware of the terrorist methods of the aggressor country," he said.

We must be prepared for an attack due to any incident, provocation or Russian strategy and attacks. At around 1:00 pm the explosion at the embassy was reported to the Spanish National Police. (1200 GMT), a police source said. According to the source, the guard "went himself to the hospital" for treatment after suffering a "minor" injury.

The source said police have launched an investigation "that includes the involvement of forensic police" without providing any additional details.

Police put up a security cordon around the embassy, ​​which is in a green residential area in northern Madrid. A man who lived opposite the embassy told AFP on condition of anonymity that he had heard an explosion.

"I thought it was gunshots. It wasn't very loud," he said.

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Ukrainian Foreign Ministry spokesman Oleg Nikolaenko said on social media after the letter bomb detonated that Ukraine's Foreign Minister Dmytro Kuleba has ordered security to be tightened at all Ukrainian embassies.

Spanish Foreign Minister José Manuel Albarés called the ambassador "to inquire about the well-being of the injured Ukrainian worker," according to a statement by Spain's foreign ministry.

Additionally, Alberes called Kuleba to offer his "solidarity and support", the statement continued.

Later that evening, a second "suspicious postal shipment" was discovered at the Instalza headquarters in the northeastern city of Zaragoza, according to the Interior Ministry. The mailed item underwent a "controlled explosion" by experts.

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Investigators are continuing to examine the detonated device and determine whether there is a connection between the incident and what happened at the Ukrainian Embassy in Madrid this morning.