Gunmen have attacked a checkpoint in the Iraqi province of Diyala, killing all five government-backed Sunni guards, security officials have said. 

The attack occurred shortly after 2am (23:00 GMT) on Saturday in the town of Khan Bani Saad, about 30km northeast of the capital, Baghdad, according to the head of the local security committee and police.

"An attack of this size, in which the five killed makes up the total (number of) staff at the checkpoint, indicates that al-Qaeda sleeper cell groups are now reactivating their movements," Saad Abdullah, head of the security committee in Khan Bani Saad, said. 

"The government should move quickly to crack down on these al-Qaeda cells." 

Frequent targets

Al-Qaeda-linked fighters are still capable of carrying out lethal attacks and there are worries they may may try to regroup following the withdrawal of US troops on December 18, nearly nine years after the invasion that toppled Saddam Hussein. 

Follow in-depth coverage of the nation in flux

Al-Qaeda's affiliate in Iraq, the Islamic State of Iraq, claimed responsibility for multiple bombings around Baghdad that killed at least 72 people on December 22. 

Members of the Sahwa, a Sunni group that took up arms against al-Qaeda and helped stop Iraq's sectarian strife becoming a full-scale civil war, are frequent targets. 

On Friday, a Sahwa member and three of his bodyguards were killed when a sticky bomb attached to their car exploded in Taji, 20km north of Baghdad, police said. 

Violence in Iraq is down from its peak in 2006 and 2007, but attacks remain common.

A total of 187 people died in violence in November, according to official figures.