ADEN: Rebel fire on a residential district of Yemen's second city Aden killed at least 20 civilians Wednesday as loyalist forces in central city Taiz launched a manhunt for 1,200 escaped prisoners.
Both cities have seen heavy fighting as loyalists of exiled President Abed Rabbou Mansour Hadi battle to fight back Houthi Shiite rebels with the support of a Saudi-led bombing campaign launched in March.
Aden was Hadi's last refuge before he fled into exile in neighboring Saudi Arabia in March and his loyalists have been battling to defend it against the rebels and renegade troops.
The Houthis and their allies pounded the loyalist-held Al-Mansura district with 15 Katyusha rockets, loyalist forces spokesman Ali al-Ahmadi told AFP.
The rocket fire began before dawn when the streets were busy ahead of the daytime fast observed by Muslims during the holy month of Ramadan, Ahmadi said.
A fresh salvo of rockets later in the morning hit mourners burying some of the dead from the earlier fire, the spokesman and witnesses said.
Medics said 41 people were also wounded, many of them seriously.
During the night, rebel positions in the nearby neighborhoods of Dar Saad and Khor Maksar had been hit by a series of Saudi-led airstrikes, residents said.
A coalition strike in neighboring Lahej province killed 13 rebels, a local official told AFP.
The air war has come under mounting international criticism.
On Monday, U.N. chief Ban Ki-moon called for an investigation after air strikes hit the U.N. Development Program compound in Aden, wounding a guard and causing serious damage.
On Tuesday Human Rights Watch said that strikes on the rebel stronghold of Saada in Yemen's northern mountains had destroyed houses, markets and a school, in what could amount to war crimes.
"The coalition's aerial bombing of Saada killed dozens of civilians, devastating entire families," said HRW Middle East and North Africa director Sarah Leah Whitson.
"These attacks appear to be serious laws of war violations that need to be properly investigated."
In Taiz, Yemen's third biggest city, loyalist forces were searching for 1,200 inmates, including Al-Qaeda members, who made a mass breakout as the prison was captured from rebel forces.
A loyalist source accused the rebels of deliberately throwing open the gates in an apparent attempt to cover their withdrawal.
"Between five and eight Al-Qaeda members were among the prisoners," a military source told AFP.
There have been repeated jailbreaks in Yemen since the Houthi rebels launched an offensive last summer, overrunning the capital and then much of the rest of the country.
Al-Qaeda's Yemen arm took advantage of the rebellion to seize the southeastern port city of Mukalla in April where it freed more than 300 inmates, including one of its leaders.
Washington regards Al-Qaeda in the Arabian Peninsula as the network's most dangerous branch and has kept up a drone war against its leaders.
But ISIS too has exploited the conflict to enter the fray in recent months, carrying out a string of deadly attacks against Shiite targets since March.
An attack claimed by the Sunni extremist group on Houthi leaders in the rebel-held capital Sanaa killed at least 28 people Monday, medics said.
The United Nations has called repeatedly for a humanitarian ceasefire to allow the delivery of desperately needed relief supplies.
U.N. envoy Ismail Ould Cheikh Ahmed renewed the appeal in talks with Hadi in the Saudi capital late Tuesday, a government source said.
"The government is coming under pressure from the United Nations for a truce," the official said.