Several international schools in Spain were checked by police with sniffer dogs while others did not open today after they received emailed bomb threats which the Interior Ministry described as being hoaxes.

A police source in Zaragoza confirmed that four international schools in the city received such threats, and that the French Lycee Moliere school did not open on Monday. At least three other British-run schools in Madrid told Reuters they had received similar threats either last week or on Monday.

In Tenerife, the French Lycee and a German international school received bomb threats and did not open on Monday, the regional government confirmed.

"Regarding the wave of threats, complaints are being taken and the investigation is being centralised. They are false threats," the Interior Ministry said in a statement.

The French embassy in Madrid confirmed emailed threats sent to several French schools and other international schools in Spain, and, although police found no suspicious objects, requested that the schools remain alert.

"The French embassy remains very vigilant... and asks all school management teams of the French school network in Spain to show increased vigilance," it said in a statement.

El Mundo newspaper said a total of 18 schools in Pontevedra, Tenerife, Zaragoza, Reus, Tarragona, Villarreal and Castellon received threats by email.

The email specified no reason for issuing the threat, a source at one school told Reuters.