Al-Jazeera Video: Top army commanders defect in Yemen

"Senior military figures, diplomats and officials in Yemen are abandoning their president of the last 32 years.

Ali Abdullah Saleh's government has been beseiged for weeks by protests in the capital Sanaa.

On Friday, more than 50 were killed in a crackdown on the streets. By Sunday, president Saleh had sacked all of his ministers.

And in the capital Sanaa, tanks rolled onto the streets, guarding the presidential Palace.

Thousands of people are protesting at the city's university, calling for a revolution.

Al Jazeera's Alan Fisher has the latest. "