The attackers were driving "about 50" four-wheel drive vehicles when they swept into the hunters` camp at dawn on Wednesday, an Iraqi source told the BBC`s Arabic service.
They struck in the Layyah area, 130km south of Samawa, after arriving from Nasiriya province, the source said.
A wide-scale search has been launched for the attackers, police say.
Hunters from various Gulf states often travel to the area at this time of year.
The hunters had been escorted by Iraqi security forces but they decided not to engage a large number of gunmen, a Samawa police colonel told the agency.
"We are talking about at least 100 gunmen armed with light and medium weapons," he said.
More than 12 years after the US-led invasion and occupation, Iraq is still plagued by violent crime and militant attacks.
In September, 16 Turkish construction workers were freed a month after being kidnapped in the capital, Baghdad, apparently by Shia Muslim militants.
Gunmen abduct Qatar hunters in Iraq desert
16 December 2015
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Gunmen have kidnapped at least 26 Qatari hunters in a desert area of Iraq near the Saudi border, officials say.
