The European Union foreign affairs chief Catherine Ashton on Friday said she was "appalled" by the attacks in the northern Lebanese city of Tripoli and called for a swift investigation.

The European Union foreign affairs chief Catherine Ashton on Friday said she was "appalled" by the attacks in the northern Lebanese city of Tripoli and called for a swift investigation.

Ashton "condemns this terrorist attack in the strongest terms and reaffirms that terrorism and any use of violence against civilians are completely unacceptable," a statement from her office said.

"She calls for a swift investigation into the events and to bring the perpetrators to justice."

Powerful car bombs exploded outside two Sunni mosques in the city, leaving 27 people dead and more than 350 wounded, the highest toll in an attack since Lebanon's 1975-1990 civil war.