Sixteen staff members at Beirut's port, the site of a massive explosion, have been detained over the deadly blast that devastated large parts of the city, a military prosecutor said Thursday.

Lebanese authorities had announced an investigation into Tuesday's explosion, which they said was triggered by a fire igniting 2,750 tonnes of ammonium nitrate stored in a warehouse at Beirut's port.

Lebanon's foreign minister said on French radio Thursday that an investigating committee had been given four days to determine responsibility for the blast, which killed more than 130 people and wounded at least 5,000.

Military prosecutor Fadi Akiki said in a statement that 18 staffers at Beirut's port had been called in for questioning, 16 of whom remain in custody pending further investigations. 

They include port and customs officials as well as maintenance workers and their managers, Akiki said.

His statement came as an official confirmed to AFP that the central bank had ordered an asset freeze for seven port and customs officials, including Badri Daher, director-general of Lebanon's customs authority.

The official spoke on the condition of anonymity because he is not authorised to speak on the issue.

A banking source confirmed to AFP that all the country's commercial banks received the order, which also lifts banking secrecy from accounts owned or linked to those in question. 

Even as they counted their dead and cleared streets of debris, many Lebanese were boiling with anger over a blast they see as the most shocking expression yet of their leadership's incompetence.

Many have raised questions as to how such a huge cargo of highly explosive material could have been left unsecured for years. 

French President Emmanuel Macron, who visited Lebanon on Thursday, called for an international enquiry, echoing demands widely supported in Lebanon and abroad for an independent probe.