Iraqi authorities on Tuesday ordered an Iranian cargo plane heading to Syria to land in Baghdad for a search, then allowed the flight to proceed after no weapons were found.

The unprecedented move appeared to be an attempt to ease U.S. concerns that Iraq is allowing Iran to fly military supplies to help Syrian President Bashar Assad battle rebel forces in his country's civil war.

Iraqi government spokesman Ali al-Dabbagh said the Iranian cargo plane was ordered to land for inspection.

"We wanted to make sure that the cargo does not include weapons," al-Dabbagh said. "Special teams searched the plane, and no weapons were spotted in the cargo."

The plane was allowed to fly on to Syria, al-Dabbagh told The Associated Press.

Last month, Iraq banned a North Korean plane from crossing Iraqi skies on suspicion it was carrying weapons to Syria.

Iraqi officials have repeatedly said that they would not allow their country to be a corridor to supply weapons to either Syrian government forces or rebels.

In violence in Iraq on Tuesday, police said five people were killed in two incidents near the disputed northern city of Kirkuk, which is home to a mix of Arabs, Kurds and Turkomen, who all are competing to control the city.

A senior police official in the city, Brig. Gen Sarhat Qadir, said three street sweepers stumbled onto a bomb on Tuesday morning as they were trying to empty a garbage bin in the nearby village of Zab. The blast killed the three workers. Kirkuk is located 290 kilometers (180 miles) north of Baghdad.

Also in Kirkuk, police found two bodies, one a district administrator in al-Wihda village.

Qadir said the two were shot dead and that an investigation was under way.

Overall, there is less violence compared to the days when Iraq neared civil war between 2006 and 2008, but deadly attacks still take place almost daily.