The workers were seized from a shop in the border town of Silopi late on Sunday by suspected members of the Kurdistan Workers Party (PKK) who then went on to attack a power plant construction site where they worked, the sources said.
There have been protests in recent months against the planned second power station in Silopi, which is being built by a Chinese company, according to the local Firat news agency, which is close to the PKK.
The Turkish military has launched an operation to try to locate and rescue the engineers, the security sources said. There was no immediate claim of responsibility.
The PKK, considered a terrorist group by Turkey, the European Union and the United States, waged a three-decade insurgency to push for greater Kurdish rights. But hostilities have largely died down since a March 2013 ceasefire.
The militants have abducted soldiers, engineers, journalists and others in the past, sometimes with the aim of securing a prisoner exchange. It was not clear why Chinese nationals were targeted in this instance.
Mutual suspicion still runs high in some parts of the southeast between Kurdish communities and the security forces in what has effectively been a militarised zone since the 1990s, and there have been isolated acts of violence.