BAGHDAD: Iraq's security situation is likely to be "turbulent" as US forces depart, with Al-Qaeda among the groups that will seek to take advantage, the top US general in the country said Monday.

"I think as we leave, you can expect to see some turbulence in security initially, and that's because you'll see various elements try to increase their freedom of movement and freedom of action," General Lloyd Austin told reporters at a roundtable in Baghdad.

"Al-Qaeda will be one of those elements," said Austin, the commanding general of US forces in Iraq.

"We expect that Al-Qaeda will continue to do what it has done in the past," he said, referring specifically to the situation in northern Iraq. "We expect that it's possible that they could even increase in their capability."

"Of course, that will depend on how effectively the Iraqi security forces and the government of Iraq are able to focus on that network."

Austin also pointed to Iranian-backed militias as a threat to stability.

"When you look at the environment in the south, we've seen activity over the last several months that are from the Iranian-backed militants," he said. "We expect that that type of activity could possibly continue into the future."

"The Iraqi government has to treat them (Shiite militias) based upon what they really are, and again, these are elements that are really focused on creating a Lebanese Hezbollah kind of organization in this country," he said.

That means "a government within a government, and those elements would have their own militia, that sort of thing. I think as we leave, if these elements are left unchecked, they will then eventually turn on the government."

"We really intend to remain engaged with Iraq," Austin said. "There's likely to be some setbacks, some tough days ahead, but I am very hopeful that we'll stay on course."

US President Barack Obama announced on October 21 that US troops would depart Iraq by year's end.

Austin said on Monday that there are less than 20,000 US soldiers left in Iraq, while eight military bases remain to be handed over.