Sani Yahaya is a religious leader who preaches coexistence between Nigeria's different religions.
The attack targeted Yahaya as he was preaching, witnesses said. Gunmen started shooting sporadically and then there was a loud blast.
Bloom Gist's Sani Umar reporting from Jos said Yahaya was known to be critical of the armed group Boko Haram, which has pledged allegiance to the Islamic State of Iraq and the Levant (ISIL) group.
"He was somebody that preached peaceful coexistence between Muslims and Christians in Plateau State," Ndege said, adding it was not clear whether Yahaya had been killed in the attack.
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Another bomb exploded at Shagalinku, a restaurant popular with politicians.
"I saw people running out crying, some with bloodstains," said resident Bashir Abdullahi, describing the scene after he said a suicide bomber ran into the crowded restaurant. "I believe many lives were lost."
Abdussalam Mohammed of the National Emergency Management Agency said 67 others were wounded in the attacks and were being treated in hospitals, according to the Associated Press news agency.
The blasts came shortly after a suicide bomber attacked a church in the restive northeastern Nigerian state of Yobe, witnesses and police said, killing five people.
Al Jazeera's Yvonne Ndege said for many Nigerians the attacks demonstrated the potent threat Boko Haram continues to pose.
"Even with all the efforts, people ask what impact there is on the ground if Boko Haram is still able to attack communities and villages in the way they have over the last few days," Ndege said.
The US has vowed to support Nigeria in the wake of Sunday's attacks.
"The United States strongly condemns the recent attacks in northeastern Nigeria inflicted by Boko Haram," state department spokesman John Kirby said in a statement.
