Three teenagers accused of pushing an elderly man to the ground at a Toowoomba taxi rank during a brazen robbery have been charged with murder.

It will be alleged the 75-year-old was critically injured when he was shoved from behind and fell face-first during a robbery about 5pm on Monday, February 6.

After a week in intensive care, the elderly man died on February 13.

The teenagers – one aged 18 and two aged 17 – on Friday had their charges upgraded to murder.

The 18-year-old Wilsonton man has been remanded in custody to re-appear in Toowoomba Magistrates on March 28.

The 17-year-old boys also remain in custody to appear in the Toowoomba Childrens Court.

Investigators continue to appeal to anyone with information or relevant dash cam footage to come forward.

-AAP