A grenade explosion has killed at least two people during Madagascar's national day celebrations in the capital Antananarivo, officials say.

About 80 people were wounded in the blast at a stadium, general Anthony Rakotoarison told AFP news agency.

President Hery Rajaonarimampianina said it was a "terrorist act", and blamed it on "political divergences".

The situation remains fragile in the country, with supporters and opponents of the president at loggerheads.

The blast happened during a free concert at the Mahamasina stadium. A military parade had been held there earlier.

It was not immediately clear who or what was behind the explosion.

In a statement broadcast on national television, the president said: "Divergences in point of view may exist between us... [But] if the leader does not suit you... you cannot kill the population," he said.

"We will never tolerate destabilisation. Especially because this is not only destabilisation but an act of terrorism."

Mr Rajaonarimampianina's election as president in 2013 brought fresh hope following years of political instability in Madagascar.

But just 18 months into his presidency, the country's National Assembly voted to impeach him for failing to deliver on his election pledges.

The bid failed but his supporters and rivals continue fighting each other.

In 2014, a grenade explosion killed a toddler and injured several other people outside the same stadium.

No arrests were made in connection with that attack and there was no claim of responsibility, AFP reported.