A peace delegation is currently in negotiations to secure the release of the Colombian international's father.
What do we know about the kidnapping?
Diaz’s mother and father were kidnapped by armed men on motorcycles from a gas station in the town of Barrancas on Saturday October 28.
A statement from the government said it was "officially aware" that the kidnapping has been "perpetrated by a unit that belongs to ELN."
Otto Patino, who leads the peace delegation, added: "We demand that the ELN releases immediately Mr Luis Manuel Diaz and we say as of now that they are entirely responsible to secure his life and integrity."
Diaz’s mother was rescued just a few hours following the kidnapping, after the police set up roadblocks around the town - which has a population of around 40,000 people and is near the country’s border with Venezuela.
Police have offered a $48,000 (€45,165 approximately) reward for information leading to Diaz’s father’s rescue.
The Liverpool forward was absent from the team’s Premier League match against Nottingham Forest on Sunday.
