Belén Carreño and Emma Pinedo wrote this article in Reuters:

Bomb disposal experts defused a letter bomb at the U.S. Embassy in Madrid on Thursday, the sixth such device sent to high-profile targets in a wave that prompted Spain to step up security and vow not to be deterred from supporting Ukraine.

The campaign began with a package sent to Prime Minister Pedro Sanchez on Nov. 24, spurring Madrid to tighten security around public buildings. Since Wednesday, similar devices have also been sent to the defence ministry, an air force base, a weapons manufacturer and the Ukrainian embassy - where a security officer was slightly injured.

Defence Minister Margarita Robles, who was visiting the Ukrainian port city of Odesa on Thursday and met her Ukrainian counterpart Oleksii Reznikov, said the letter bombs would not deter Spain from supporting Ukraine's "just cause".

"What must be very clear is that none of these deliveries or any other violent action will change the clear and firm commitment of Spain, NATO countries and the European Union to support Ukraine," she said.

The latest package was intercepted at the U.S. Embassy by security officials and was later detonated in a controlled explosion by Spanish police.

On Wednesday, a package addressed to the Ukrainian ambassador to Spain detonated at the country's embassy as a security official investigated it, causing him to suffer minor injuries to his hands and a concussion. Security has now been stepped up around embassies as well.

Later on Wednesday, Instalaza, an arms manufacturer in Zaragoza, northeastern Spain, that has send more than 1,000 C90 rocket launchers to Ukraine received another package. On Thursday an air force base housing a European Union satellite centre, Spain's defence ministry and the U.S. Embassy also received packages.