Spanish Prime Minister Pedro Sanchez's office received on November 24 a letter containing an explosive device "similar" to the ones received by the Ukrainian embassy, a Spanish weapons manufacturer on Wednesday and an air force base on Thursday, the Interior Ministry said.

Security around public and diplomatic buildings are to be stepped up after a series of letter-bombs were received around the country, the ministry added. (Reporting by Inti Landauro, Belen Carreno and Emma Pinedo)