18 hurt in blast at restaurant in southern Philippines

An extortion letter had been sent to the restaurant owner last week.

A bomb exploded at a restaurant in the southern Philippines on Wednesday, wounding at least 18 people in a suspected revenge attack by a militant group, security officials said.  
There was no immediate claim of responsibility for the blast on the southern island of Mindanao, a region troubled by banditry and armed rebellions.
"This could be an effort to avenge their losses. We have neutralised many of their members in our relentless operations," Sobejana told reporters.
Another possible motive for the attack was an extortion letter sent to the restaurant owner last week, he said.
Government forces have in recent months pursued members of the militant group in central Mindanao. The BIFF was blamed for a blast in August and another bombing in September in Isulan that killed five people and wounded dozens.  

• Philippines