The blast took place a little after midnight (2200 GMT on Thursday) in the Belgium's Chimay.
A suspected gas explosion at a sports centre in southern Belgium killed one person and seriously injured two others, a security official told the Belga news agency on Friday.
The blast took place a little after midnight (2200 GMT on Thursday) in the small town of Chimay, 110 kilometres south of Brussels. The official said five people were in the building at the time, with the remaining two victims only slightly injured.
A fire rescue official in Chimay told AFP that they suspected the blast was caused by exploding gas cannisters inside the premises, but the official cause remains unknown and an investigation is underway.
The explosion occurred as Belgium remains on high alert after suicide bombers struck Brussels airport and a metro station near the European Union headquarters on March 22, killing 32 people.
Those attacks were claimed by the ISIS group, which controls large areas of territory in Iraq and Syria and has claimed numerous terror attacks in Europe in recent months.