The students have not been attending classes for up to six weeks now after they first boycotted classes on May 2.
Classes were then suspended for an indefinite period by the university council on May 20.
The suspension lasted for 10 days and students were asked to return to classes to continue semester one on June 13, which was a public holiday.
This was so classes would kick off on Tuesday, June 14, while the medical students were told to commence classes on June 6.
However, this did not eventuate following the shooting of students by police on June 8 during an attempted peaceful protest to Parliament.
This left four male students admitted to hospital with bullet wounds while several others suffered minor injuries.
The students are now in mourning and stated last week that they will not return to class until their colleagues are released from hospital.
UPNG acting chancellor Dr Nicholas Mann says students must return to classes on Monday onward to secure their semester one of 2016.
Dr Mann said today that they must return to class for the sake of their own future.
“Semester one of 2016 will not be viable after June 25 if students don’t attend class,” Dr Mann said.