SANAA, Yemen (AP) -- Yemeni government forces fired mortars on Wednesday at a central district of the capital Sanaa where tens of thousands of opposition supporters had gathered, killing three and wounding at least 16 people.
Also in Sanaa, the headquarters of the renegade 1st Armored Division, came under heavy shelling from government forces but there were no immediate reports of casualties, according to the officials.
Wednesday's violence breached a cease-fire negotiated a day earlier to end a deadly bout of violence between government forces and opponents of the regime. More than 70 people have died in Sanaa and elsewhere in Yemen so far this week.
The officials said the shelling targeted a part of Change square, where protesters have camped out since February to demand the ouster of longtime President Ali Abdullah Saleh.
The officials spoke on condition of anonymity because they were not authorized to speak to the media.
The 1st Armored Division, perhaps Yemen's most combat tested military outfit, mutinied in March to join the opposition. It is led by Saleh's one-time confidant and war veteran Maj. Gen. Ali Mohsen al-Ahmar.
The targeting of the division's headquarters is the latest indication that the fight over control of the Yemeni capital will primarily pit the rebel unit against the elite Republican Guards, led by Ali's son and one-time heir apparent Ahmed. Both sides claim about 20,000 fighters inside the capital, but the Guards have superior weaponry. However, military experts say the final showdown between them would be won by the side that shows better urban warfare techniques.
The resumption of violence followed a brief lull in the fighting that allowed Sanaa residents to venture out from their homes on Wednesday morning to buy food and other essential supplies. Many hurried back home as an outburst of heavy gunfire rang out from an area close to the residence of the country's vice president.
Yemen's turmoil began in February as the unrest spreading throughout the Arab world set off largely peaceful protests in the deeply impoverished and unstable corner of the Arabian Peninsula that is also home to an al-Qaida offshoot blamed for several nearly successful attempts to attack the United States.
The government has responded with a heavy crackdown, with hundreds killed and thousands wounded.
Saleh went to Saudi Arabia for medical treatment after a June attack on his Sanaa compound and has not returned to Yemen yet. He has resisted calls to resign, backing off in the last minute on at least three occasions from signing a proposal by Yemen's Gulf Arab neighbors and endorsed by the United States for him to step down in exchange for immunity.