The dead included 96 killed as they sought shelter at the downtown fuel stop during a torrential rain storm that battered Accra for more than five hours on Wednesday night.
Thousands have been made homeless by the flooding.
Ghanian President John Mahama declared three days of mourning from Monday and announced a $12 million relief and rebuilding fund.
“This loss of life is catastrophic, almost unprecedented,” Mahama said, according to Starr FM radio station. “A lot of people have lost their lives. I am at a loss of words to express how I feel. Many of them through the floods and many still through the fire incident as a result of the explosion that took place.”
The petrol station blast - caused by a fuel leak - saw those sheltering on the station’s covered forecourt killed in a fierce fireball and nearby buildings destroyed.
Residents had taken refuge on high ground to escape the floods as vehicles and buildings were submerged. Thousands of passengers were stranded and hundreds of people spent the night at their work places and on rooftops.
Local radio stations were inundated with distress calls and the National Disaster Management Organization conducted evacuation missions by boat.
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