In the 2.30pm incident, the duo, wearing helmets, used an axe to smash glass showcases displaying jewellery and took off with several trays of jewellery.
Penang Police Chief Abdul Ghafar Rajab said they escaped on a motorcycle parked near Komtar in Jalan Teck Soon.
He said there were several workers on duty but no customers at the time of the hold-up.
He was speaking after witnessing a handing-over of duties ceremony between outgoing state police deputy chief, A Thaiveegan, and his successor, Roslee Chik here.
Thaiveegan will assume the post of Commercial Crime Investigation Department deputy director at the federal police headquarters in Bukit Aman.
Roslee was formerly Bukit Aman Anti-Vice, Gaming and Secret Societies principal assistant director.
Abdul Ghafar said police would review the closed-circuit television (CCTV) camera recording at the premises, which was unmanned by security guards, to facilitate investigations.
Adjoining jewellery shop owner Saodah Saad, 42, said she heard shouting and the sound of shattered glass before seeing a couple fleeing with some packages.
“I saw a couple walking in front of my jewellery shop but I did not notice anything suspicious. We (she and two workers) only found out about the robbery when we heard people shouting for help and saw the couple running away.
“We can’t believe they dared to rob in broad daylight as all shops here are equipped with CCTVs,” she said.