Violence erupted in Yemen's capital again Wednesday despite a truce declared overnight, witnesses told the AFP.

Saying rockets and shelling shook  Sanaa overnight as residents found themselves amid renewed fighting between rival military units that killed at least dozens on Tuesday.

The fighting initially broke out Tuesday and two days of minor skirmishing between protesters and security forces when demonstrators laid seige to a military installation in Saana held by loyalists of the Republican Guard.

Army defectors engaged the besieged soldiers in an extended firefight lasting hours before the defenders quit the installation.

According to reports sniper-fire from rooftops, and two stray rockets that smashed into a field hospital, accounted for many of those wounded.

Wednesday's fighting erupted in a central street of Sanaa whose residents include Vice President Abdrabuh Mansur Hadi, who had late on Tuesday declared the truce.

The renewed fighting comes despite Yemeni president Ali Abdullah Saleh announcing he will not return to the country and authorizing Hadi to negotiate a transfer of power agreement.

Western and Gulf diplomats expect a Gulf Cooperation Council-brokered transfer of power agreement to be signed within days.

According to Al Jazeera, citing medics in the city, at least 76 had been killed since Sunday.