Around 40 foreign suicide bombers enter Iraq each month, Prime Minister Haider al-Abadi said on Monday, calling for countries in the region to curb the flow of foreign fighters.

Suicide bombers are one of the deadliest weapons of the Islamic State (IS) jihadist group, which deploys them in explosives-packed vehicles to breach Iraqi defences or cause mass civilian casualties in crowded areas.

"An average of 40 suicide (bombers) enter Iraq per month," Abadi said in televised remarks.

"The number of foreign fighters in Iraq now exceeds the number of Iraqis" in IS, Abadi said, and there are suicide bombers "from every country" in the region.

"There is a problem to be addressed by these countries," Abadi said.

"It is up to others... to stop these terrorists from coming to our country, and to stop this machine of killing and destruction and terrorism."

IS launched a brutally effective offensive last June that overran a third of Iraq, including swathes of its border with Syria where the group also holds significant territory, making it easy for fighters to enter the country.