Anti-government protesters against Yemen's President Ali Abdullah Saleh in the southern city of Taez (Photo: Reuters)
A nine year-old child was among the six killed in the city of Taez, as a medical source confirms, "The bombing killed six people this morning (Friday), all of them civilians, and wounded dozens of others who were taken to the hospital."
Security forces began operations shortly after midnight (2100 GMT Thursday) in the area of Freedom Square, where demonstrators had rallied to call for the fall of the regime, witnesses told AFP.
Residents said the shelling intensified on Friday morning, focusing on the neighbourhoods of al-Rawdah and Zeid al-Mushky in Taez, which have been at the forefront of anti-regime protests.
On Thursday, one man was killed and nine other people were wounded in Taez, said medics.
Witnesses said Republican Guard troops, commanded by Saleh's son Ahmed, fired artillery rounds into the centre of Taez where tens of thousands of protesters were calling for the veteran leader's prosecution.
The escalation in violence coincides with the return of the UN envoy to Yemen, Jamal Benomar, to revive efforts aimed at resolving the country's political turmoil.
Benomar, who arrived in Sanaa on Thursday, began meeting with several government and opposition figures to discuss recent developments and the best means for resolving the current crisis.
"My visit came to reach a political reconciliation and to sign the Gulf initiative" by which President Ali Abdullah Saleh will step down in return for immunity from prosecution for himself and his family, Benomar told reporters upon his arrival.
Officials of the ruling party and delegates negotiating on behalf of the opposition told AFP on Thursday the talks were making progress.