Yemeni officers run to help their fallen comrades after they hear a large explosion during a military parade rehearsal

Scores were killed by the blast caused by a suicide bomber, dressed in army uniform.

More than 90 people were killed and 60 wounded ... and the death toll is rising.

Officers were horrified by the scene:

(SOUNDBITE) (Arabic) MILITARY BATTALION OFFICER SALIM AL-WASIE'I, SAYING:

"We deplore this criminal act, this is a massacre. We were standing in the military parade, getting ready for the next stage, when we suddenly heard a strong explosion, and we saw blood and legs flying everywhere, arms and legs flying in the air. The information we have from the hospital is that there are between 80 and 100 casualties, including both dead and injured."

Military sources say Yemen's defence minister and chief of staff were present, but were unhurt in the blast.

The explosion coincided with a U.S.-backed offensive against al-Qaeda-linked militants in the south, which has seen heavy fighting over the weekend.

The parade was set to be part of Yemen's national day celebration scheduled for Tuesday to commemorate the unification of the north and south.

Jessica Gray, Reuters