Saturday's attack brought the toll to more than 130 in three days of violence in Iraq.
The tent was on a public square in the town of Abu Saydah, 100km from the capital, Baghdad.
Mourners in Iraq traditionally erect a tent outside their home to receive relatives and friends offering their condolences.
Earlier on Saturday a car bomb exploded near a market outside Baghdad, killing at least 13 people and wounding 21.
The morning explosion occurred near the Diyala Bridge area just southeast of Baghdad as dozens of people were shopping at the popular market, police Colonel Nouri Ashour said. The dead included five women, he added.
The attacks came a day after 78 Shia worshippers died and 90 were wounded when two bombers blew themselves up inside two mosques during prayers in the mainly Kurdish town of Khanaqin, an hour away from Abu Saydah, near the Iranian border.
US soldiers killed
Near Baiji, north of Baghdad, five US soldiers were killed in two separate bomb attacks on Saturday near Baiji, the US army said.
The latest attacks increase US
casualties to a total of 2086
"Five soldiers from the 3rd Brigade Combat Team, 101st Airborne Division were killed in action, and five were wounded ... in two separate improvised explosive device attacks" on patrols near Baiji, 200 km from the capital, a statement said.
"Three of the injured were transported to nearby military medical facilities, and two were treated and returned to duty." the statement added.
Meanwhile, an Iraq police source in Baiji said a US-Iraqi patrol was attacked at around 5:00 pm (1400 GMT) on Saturday.
He said one policeman was killed and fours other wounded, and that a US Humvee had been destroyed. He gave no details on US casualties.
The lastest US deaths bring to at least 2086 the number of US military personnel killed in Iraq since the March 2003 invasion, according to an AFP tally based on the independent Iraq Coalition Casualty Count.