Chisinau — A grenade blast in the heart of the Moldovan capital wounded more than 40 people among thousands at a late night outdoor concert, authorities said Thursday.

"There is no doubt that this was a terrorist act whose aim was to frighten the population," Interior Minister Viktor Katan told reporters

He said an investigation had shown that the blast late Wednesday was caused by a grenade of the kind used by the military but did not give further details of the aims of the attack.

Chisinau’s central square was filled with young people attending a concert that included acts from Moldova, Romania and Russia.

Prime Minister Vlad Filat had received threatening telephone calls just before the explosion, his spokesman said.

"The calls have been traced. An investigation is in progress. The calls came from abroad," Katan added, without giving further details.

A criminal investigation for terrorism has been started into the blast, Valery Zubko, Moldova’s general prosecutor told reporters.

Amplifying tension in the capital, a man claiming to carry a grenade threatened to blow himself up outside the prosecutors office just before a briefing on the explosion was due to take place there.

An AFP correspondent said the man was dressed in black and was carrying a black bag which he claimed carried a grenade. A large crowd of journalists stood at the scene waiting for the briefing.

The man, who officials said was demanding the release of his son from jail, gave himself up after around one hour.

Of the 41 wounded, 12 were still hospitalized on Thursday with leg wounds and stomach and facial injuries, Katan said. There were no reports of fatalities.

"All wounded and eyewitnesses were questioned. A portrait of the suspect has been formed, a young man of 25 years," said Katan.

Moldova, Europe’s poorest country, was rocked by riots in April after disputed legislative elections provoked riots in the capital that the then Communist authorities blamed on neighbouring Romania.

The Communists lost a re-run of the elections in July and a liberal pro-European Union government has now taken office although there remains stalemate over the identity of its next president.

New prime minister Filat is a champion of closer integration with the EU and his rise to power has been observed with anxiety in Moldova’s former Soviet master Moscow.

Vladimir Voronin, the strongman who led the country in the last eight years of Communist rule, has already stepped down as president but has accused the new government of being incapable of leading the country.

The explosion initially did not interrupt the concert, which carried on for another 30 minutes before police ordered it to end.

Chisinau mayor Dorin Chirtoaca said the concert had continued to ensure there was no panic.

Police halted traffic along the capital’s main Stefan Cel Mare Avenue but the street reopened in the morning.

As well as poverty, the country has also grappled with the problem of its breakaway province of Transdnestr which declared unilateral independence from Moldova in 1990 but has never obtained international recognition.

AFP/Expatica