Dozens of Chinese workers have been relocated from strife-torn northern Iraq, state media said Friday, with an additional 1,200 set to depart in the coming days.

More than 50 China Machinery Engineering Corp (CMEC) workers arrived in Baghdad by helicopter from northern Iraq on Wednesday night, the state-run China Daily newspaper reported.

Another 1,200 trapped in the northern city of Samarra will arrive in Baghdad by bus "within three days", the report added.

Militants from the jihadist group the Islamic State of Iraq and the Levant (ISIL) have spearheaded a lightning offensive that has captured swathes of territory north and west of Baghdad this month.

China -- the largest foreign investor in Iraq's oil industry -- has more than 10,000 workers on a wide range of projects in the country, officials say, although most are in the south, far from the current fighting.

Even so, major Chinese oil firms have prepared evacuation plans in case the assault threatens their operations, highlighting the risks to energy supplies for the Asian giant.

Resources are a key interest for China, the world's second-largest economy, and Iraq is its fifth-largest source of crude oil imports.

At a regular briefing Thursday, a Chinese foreign ministry spokeswoman denied reports that efforts to evacuate some of the workers this week had failed.

The financial magazine Caixin reported that Iraqi troops had turned away buses of CMEC workers near Baghdad and forced them to return to Samarra.

"The Chinese embassy in Iraq is proceeding with the close cooperation with the Iraqi government and the army on a precise assessment of the security situation so as to guarantee a swift, secure and orderly evacuation of Chinese personnel," Chinese foreign ministry spokeswoman Hua Chunying said.