The government blamed Shia fighters loyal to Abdul-Malik al-Huthi for Friday's blast and said six people had been arrested.
"Those who carried out this ugly crime are terrorists and criminals linked to the terrorist Abdul-Malik al-Huthi," an interior ministry statement said, referring to the brother of the late commander.
However, the group has denied any responsibility.
Al-Huthi told Al Jazeera: "We condemn this regrettable incident and deny categorically any role in this incident.
"It is not part of our ethics to target mosques or worshippers at all."
The renewed violence comes despite efforts to implement a peace deal between the government and the fighters, brokered by Qatar in June 2007.
The agreement, under which the fighters would lay down their arms, was revived during a meeting between the two sides in Doha in February.