Spain rocked by wave of letter bombs, with the country's prime minister among those targeted

• Spain's prime minister was targeted by a letter bomb, the interior ministry said on Thursday.
• The envelope and its contents were similar to those used in four other incidents, it said.

Spain has been rocked by a spate of letter bombs that have targeted the country's prime minister and military-related sites, as well as Ukraine's embassy in the country.

Spain's interior ministry said in a statement on Thursday that an envelope containing explosives was addressed to Prime Minister Pedro Sánchez, and was detected and neutralized by his security services.

It added that the envelope was received on November 24, and that the envelope and its contents were "similar" to those sent to other targets in Spain.

One was sent to the Ukrainian embassy in the capital city Madrid, which exploded on Wednesday, with an embassy worker receiving minor injuries, the ministry said.

Another was sent to an air base in Madrid, and another to the headquarters of Instalaza, a military equipment company in the northern city of Zaragoza. Spain's defense ministry also said it had been targeted.

According to The Guardian, Instalaza has been manufacturing rocket launchers that have been sent to Ukraine.

Investigations are underway, the interior ministry said.

A government official said that the letter sent to the Instalaza headquarters, which was neutralized by the national police, and the one sent to the Ukraine embassy had the same email address written down as the sender, The Associated Press reported.

Another envelope was detonated by security at the Ministry of Defense headquarters on Thursday, which was addressed to the defense minister, Spain's Secretary of State for Security said, according to Spanish newspaper El Pais.

Spain has ramped up security around public buildings in response, the interior ministry said.

On Wednesday Ukraine's Foreign Affairs Minister Dmytro Kuleba ordered security to be beefed up at all Ukrainian embassies around the world, following the explosion at the Madrid address.