Yemeni security officials say thousands have protested in the capital against "excesses" by security forces, calling for the overthrow of the president and national security apparatus.

The demonstration came during the funeral of 13 Shiite protesters who were killed in clashes with police last Sunday. The protesters had been demanding the release of political detainees, and attempted to storm intelligence headquarters in Sanaa.

Also on Thursday, Human Rights Watch called on the government to thoroughly investigate Sunday's incident and hold the culprits responsible.

Shiite rebels of the Hawthi tribal group have waged an on-and-off uprising against the government for years.

Hawthi leader Ali al-Bokhayti said security forces had handled the protesters as if they were armed, a charge he denied, saying that "all the victims were from one side."