BAGHDAD, Iraq (CNN) -- A judge and three members of a group opposing al Qaeda in Iraq were shot to death Monday in Iraq's Diyala province, a local security official said.
The three members of a local Awakening Council were killed as they stood by a vegetable vendor's stall in Mafrag, west of Baquba, Diyala's capital, the official said.
Such councils are part of the "awakening" movement in Iraq, a grassroots front of locals who oppose al Qaeda in Iraq. They are predominantly Sunni and sometimes include former militants. Many of the members have been recruited by the U.S. military's "Concerned Local Citizens Program" to work against al Qaeda in Iraq.
Monday's shootings came just hours after Osama bin Laden's top lieutenant warned that Iraqi tribal leaders who side with U.S. troops against al Qaeda fighters would face reprisals when Americans leave Iraq.
In a video statement released Sunday, Ayman al-Zawahiri called tribal leaders who cooperate with Americans "scum" and "traitors."
"I warn those individuals from among the armed factions who have been involved in cooperation against the Mujahedeen that history is recording everything, and that they will lose both their religion and life," al-Zawahiri said.
Earlier this month, a message from a member of al Qaeda in Iraq called Awakening Council members traitors and urged attacks on them.
In Baghdad on Saturday, Awakening Council members were attacked in two incidents. Two were killed and 10 were wounded in a roadside bombing, and two others were wounded when gunmen opened fire on a checkpoint manned by Awakening Council members in southern Baghdad.
The judge killed Monday in Diyala province was shot while driving to work.
Diyala, north and east of Baghdad, has long been plagued by violence and has been the scene of much fighting since the United States began its troop increase called the "surge."
The U.S. military has said insurgents have fled to Diyala province from other areas in Iraq. U.S. and Iraqi forces have launched offensives against them in the region, one of the so-called Baghdad "belts" targeted in the "surge."
The outgoing Army commander of U.S. troops in Baghdad on Monday pointed to a wide range of security improvements in the Iraqi capital, from a drop in attacks to support from grass-roots citizen volunteers.
But Maj. Gen. Joseph F. Fil Jr., commanding general of Multi-National Division-Baghdad and the 1st Cavalry Division, emphasized the riskiness of swift coalition troop pullouts, saying that despite progress, the local forces are unprepared to "stand entirely on their own."
"I want to be absolutely clear that while we have seen significant progress during our tour here, we are very mindful that it is fragile and there is very tough work ahead. Al Qaeda is down but is by no means out," said Fil, briefing Pentagon reporters from the Iraqi capital.
The authority for Multi-National Division-Baghdad will be transferred Wednesday to the 4th Infantry Division, with Maj. Gen. Jeffery Hammond assuming command from Fil. After 15 months in Baghdad, the 1st Cavalry Division is returning to Fort Hood, Texas.
CNN's Jomana Karadsheh and Roya Shadravan contributed to this report.