Gunmen on Wednesday kidnapped 11 Iraqi pilgrims travelling in a minibus on their way to the holy Shiite city of Karbala for a religious festival, a police officer said.

"Gunmen stopped them and took them with the bus onto a dirt road," Hilla police Lieutenant Kadhim al-Salami said, adding that the driver was also kidnapped, citing witness accounts.

The kidnapping was the first in the region for around two years.

The minibus was stopped on a highway near the town of Abu Gharak on its way to Karbala for commemoration ceremonies marking the birth of Imam Mahdi, an 8th century Islamic leader who vanished and who is revered by Shiites as the coming Messiah.

Tens of thousand of Shiites are expected to converge on the shrine city of Karbala, 110 kilometres south of Baghdad, for Friday's ceremonies.

Iraq's police and army took over full responsibility for security in the country's cities and towns when US forces pulled out of urban areas on June 30, as part of a security accord between Baghdad and Washington.

But Iraqi forces have been handling security at the Karbala ceremonies for the past several years.