The bodies of those killed, including seven women and four children, were taken overnight to the morgue at a public hospital in Taez, said the medical officials.
Several other civilians were wounded and hospitalised.
The Shiite Huthi rebels and their allies had fired Katyusha rockets on Sunday targeting the district in central Taez, according to medics and residents.
Viewed as the key to controlling the capital Sanaa, Taez has been the scene of deadly fighting between the rebels and loyalists of Yemen's exiled government.
Pro-government forces claim to control "75 per cent" of the city, including the presidential palace and the residence of former president Ali Abdullah Saleh -- whose supporters are fighting among Huthi ranks.
But this could not be confirmed from independent sources.
Meanwhile, Saudi-led warplanes carried out several strikes Monday against rebel positions in the province of Marib, east of Sanaa, officials said.
One official said up to 53 Huthis were killed in the raids, but there was no independent confirmation of the report.
The Huthis have seized control of large parts of the country including Sanaa, forcing President Abedrabbo Mansour Hadi to flee to the southern port city of Aden and then Saudi Arabia.
In March, Saudi Arabia launched a coalition that has been carrying out an air war against them.
The kingdom, as well as the United Arab Emirates, have also backed pro-government forces with arms and troops.
Riyadh accuses Tehran of arming the Huthis, a charge it denies.