Armed assailants struck during the night on Friday, killing residents and burning homes.
The army and a local civil rights group blamed the Allied Democratic Forces.
It's not clear how many people have died, but thousands have fled.
"It might stop before or go on. It's difficult to forecast."
He was one of 8000 migrants who swam or climbed over a border fence into Ceuta this week.
"It is like crop rotation in farming... my duty is to satisfy my wives. I know each of them personally and I satisfy them accordingly."
His campaign said on Monday he was joining troops battling what he called terrorists.
Compaore went on to rule Burkina Faso for 27 years before being ousted in a 2014 uprising.
About 30 percent of the world's shipping container volume moves through the Suez Canal daily.