Thousands of demonstraters gathering in downtown Baghdad Saturday,
Violence escalating as security forces began fiing teargas,
With reports of one policeman killed and seven other wounded in clashes.
These protesters loyal to Shi'ite cleric Moqtada al-Sadr demanding political reforms -
Iraqi security forces pushing back as they approached the heavily fortified Green Zone, which houses government buildings and embassies.
The demonstrators want an overhaul of the commission that supervises elections ahead of a provincial vote due in September.
Sadr suspects that members of this commission are loyal to his Shi'ite rival, former Prime Minister Nuri al-Maliki, one of the closest allies of Iran in Iraq.
He said his supporters wanted to go near the Green Zone to make their voices heard, but then asked them to quote "withdraw until further notice".
The escalation of problems with the prominent cleric comes at a bad time for Prime Minister Haider al-Abadi,
Who wants to keep the focus on dislodging Islamic State from Mosul.