Seven women and five men have been shot dead in a brothel in Baghdad, state and medical officials say.
Unknown armed gunmen are said to have burst into the brothel in the well-to-do eastern district of Zayouna on Wednesday afternoon and opened fire.
Prostitution is prohibited under Islam, the dominant religion in Iraq.
The killings come two days after multiple bombings killed at least 70 people – more died in fresh blasts on Tuesday.
In recent months Iraq has seen a rise in attacks linked to growing political and sectarian tension.
The escalation of violence has raised fears of a return to the carnage of 2006-7.
In response, Prime Minister Nouri al-Maliki has ordered a shake-up in senior military ranks across the country, reports said.
Zayouna, where Wednesday’s attack took place, is a mixed district of Sunni and Shia Muslims.
Only a week ago, a row of alcohol shops in the district was attacked by gunmen. Ten Christians working in the shops were killed, while customers were allowed to leave unharmed.