ABUJA, Nigeria — Suspected Islamic militants have struck for a fourth time in three days in Nigeria, killing 20 people including a traditional ruler in attacks in the northeast, local government and security officials said Wednesday.

The unprecedented string of attacks, which started with a massive explosion in the capital that killed at least 75 people, has many questioning the ability of Nigeria’s military to contain the 5-year-old Islamic uprising. It has killed more than 1,500 people this year alone, compared to an estimated 3,600 between 2010 and 2013.

“Once again, the sophisticated methods of the bombers and insurgents, the audacity of their open attacks and the devastating stealth with which they operate … calls into question the strategy of the Nigerian security forces and their commitment to the fight,” The Guardian newspaper of Nigeria said in an editorial Wednesday.

“As Nigeria bleeds all over, a more heart-rending phenomenon is the politicization of the insurgency,” the independent and authoritative newspaper said. “The ruling elite seems conscienceless enough to be exploiting the crisis, in symbols and in substance.”

Just last week the emir of embattled Gwoza district had appealed to the government to “save our souls,” saying his people are being attacked daily.

By Tuesday, one of his local monarchs was dead.