Five letter bombs detected in Spain, including to PM's office as country steps up security

Bomb disposal experts have defused a fifth letter bomb as Spain steps up security to confront a spate of explosive devices sent to high-profile targets, including the Prime Minister and the Ukrainian ambassador in Madrid.

Key points:

• Spain says the homemade devices contained a flammable powder and trip-wire that would generate "sudden flames" rather than an explosion

• An envelope addressed to PM Pedro Sanchez was received on November 24 and disarmed by his security team

• Police have been ordered to strengthen security around public buildings and to check postal deliveries carefully

Early indications suggest that all five of the packages were sent from within Spain, the country's Deputy Interior Minister told journalists on Thursday.

Rafael Perez, the junior minister responsible for security, said the homemade devices were sent in brown packages containing a flammable powder and trip-wire that would generate "sudden flames" rather than an explosion.

The packages were addressed to the heads of the institutions they were sent to.

Mr Perez said one of the devices had detonated — injuring a security officer at the Ukrainian embassy in Madrid, three others were detonated by the security forces in controlled explosions and one had been kept intact for investigative purposes.

"It appears that they were all sent from within the country but we are basing this on early visual inspections without yet having an in-depth technical report," he said.

Mr Perez said it did not yet appear necessary to convene the security committee that would evaluate stepping up Spain's terrorist threat level, which is already at the second-highest level following terror attacks around Europe in the past decade.