A bomb squad in Madrid has safely destroyed a grenade that police believe was thrown over the wall of a migrant centre for children.

The grenade was found on Wednesday morning on the patio of the centre, in the Hortaleza area of Spain’s capital.

Police said it was a training grenade that contained a small amount of explosives.

The centre was evacuated while experts carried out a controlled explosion. No injuries were reported.

Dozens of unaccompanied minors, many of them immigrants, are reported to be housed at the residential centre.

Spanish authorities are investigating the incident but police are yet to identify any suspects or establish a motive.