Bangladesh has been experiencing heat waves across the country, with a high of 41.5 degrees Celsius in Chuadanga on Friday
A new date for the exams will be announced later, he said.
Like in the past five weeks, the BNP issued a statement on Tuesday, extending the 72-hour shutdown from Sunday to 6am on Friday.
Through February so far, the exams were held on seven weekly holidays on Fridays and Saturdays.
The education ministry had to defer 13 exams and announce fresh dates or promised to do so soon.
Around 1.5 million students from 27,808 educational institutions are taking this year’s SSC exams.