The blast hit a post of the Huthis' police force in the Hayel district of Sanaa, the official said.
It came a day after a bombing claimed by Al-Qaeda killed four people, including a journalist, at a Huthi gathering in the mainly Shiite city of Dhamar, south of the capital.
On Thursday, a suicide bomber killed 49 people at a religious celebration organised by Huthi supporters in the militia-held but mainly Sunni city of Ibb further south.
Yemen has been dogged by instability since an uprising forced longtime strongman Ali Abdullah Saleh from power in 2012, with the Huthis and Al-Qaeda seeking to fill the power vacuum.