Editor's note: This story has been updated on NavyTimes.com.
An American service member was killed in northern Iraq on Thursday, the fourth troop killed in combat since American forces returned to Iraq in 2014.
The service member, whose name will be released after their family is notified, was killed by an improvised explosive device in operations in northern Iraq, defense officials said.
Officials told the Associated Press that the service member was fatally wounded near the town of Bashiqa, north of Mosul, and was operating as an explosive ordnance disposal specialist in support of Kurdish peshmerga. The officials spoke to the Associated Press on condition of anonymity because they were not authorized to publicly discuss details.
Thousands of American forces are involved in the invasion of Mosul that began Monday in northern Iraq. Mosul is the Islamic State group's capital in Iraq and U.S. officials say it's heavily fortified with improvised explosive devices.
There are about 5,000 American troops deployed in Iraq, many of them advising and assisting the Iraqi military. More than 100 are embedded with forward-deployed Iraqi forces, military officials said.
The service member was the second killed this week. A service member deployed to Afghanistan was shot and killed Wednesday by an Afghan wearing a military uniform. U.S. defense officials said the Afghan gunman opened fire on a group of Americans at Camp Morehead, a military base near Kabul.
It's unclear whether the service member in Iraq was killed while operating with Iraqi government forces or Kurdish peshmerga.
Pentagon spokesman Peter Cook said Tuesday that American forces are not on the front lines, but remain at risk.
"We've been clear from the start that Americans are again playing an advisory role -- an enabler role for these Iraqi forces. It will be Iraqis in the lead with Americans in a support role. Most of the American forces in Iraq are not anywhere close to the front line. That is the way this has been structured. Many of them are in logistical support roles. Many of them are carrying out training missions, for example, that are well away from Mosul," Cook said at a press briefing.
"But that doesn't mean that there is not a risk to Americans. We have seen that demonstrated already in Iraq. We're very aware of that and there -- we're taking steps, we -- as many steps as we can to reduce the risk to American forces and we'll continue to do that," Cook said.
The other Americans killed in hostile action in Iraq since U.S. troops returned there in 2014:
- Navy SEAL Charles Keating IV was killed in a raid alongside Iraqi troops on May 3, 2016.
- Marine Staff Sgt. Louis Cardin was killed by a rocket attack on March 19 when he was deployed to an artillery outpost near the Iraqi town of Makhmour.
- Army Master Sgt. Joshua Wheeler was killed during a raid on Oct. 22, 2015.