The death toll from an explosion at a bustling market in the Armenian capital Yerevan rose to six on Monday as search operations continued for people believed trapped under rubble.

Another 61 people were injured and 15 were missing after Sunday's blast that led to the collapse of a building at the Surmalu wholesale market, Armenia's Emergency Situations Minister Armen Pambukhchyan said.

Rescue operations were continuing  "very carefully" with people still believed to be trapped beneath the debris, he added.

Pambukhchyan told reporters that video footage of the incident showed that "there can be no talk of a terrorist attack" as the fire started before the explosion.

He said the fire spread to "pyro materials". Local media had earlier said the explosion went off at a place that stored fireworks.

The cause of the fire was being established.

The minister said that smoke and small fire could persist for several more days with lots of plastic smouldering at the scene.

Photos and videos posted on social media after the blast showed a thick column of black smoke over the market and what appeared to be a series of detonations can be heard.

Prosecutors meanwhile launched a probe into violations "on stocking inflammable goods", breaches in fire safety standards and the death of people "due to negligence".

Armenia's Prime Minister Nikol Pashinyan visited the site of the blast on Monday, according to his press service.

In all, 200 firefighters and medical workers were sent to the scene, as well as fire engines and construction site equipment.

Rescue workers used a digger to clear away rubble, an AFP journalist at the scene reported earlier.

The disaster comes as the country of three million people is still recovering from a 2020 war with Azerbaijan, which ended in a heavy defeat and sparked a political crisis.