Families of victims killed in the 2020 Beirut explosion rallied Thursday to support the judge investigating the disaster, after he was charged by Lebanon's top prosecutor in the highly politically case.

Security was tight at the palace of justice in Beirut, where dozens of family members of the victims gathered "to support the investigation" led by investigative judge Tarek Bitar.

One of history's biggest non-nuclear explosions, the August 4, 2020 blast destroyed much of the Lebanese capital's port and surrounding areas, killing more than 215 people and injuring over 6,500. No official has been held accountable for the disaster.

Bitar this week defied Lebanon's entrenched ruling elite by daring to charge several powerful figures -- including prosecutor general Ghassan Oueidat -- over the blast, and revived a probe that was suspended for over a year amid vehement political and legal pushback.

Oueidat in turn charged Bitar for insubordination and for "usurping power," calling him for questioning on Thursday -- a summons Bitar is not expected to attend.

He also ordered the release of all those detained in the case, and slapped a travel ban on Bitar.

The organisation of families of those killed called the move against Bitar a "political, security and judicial coup d'etat".

Relatives of the victims and rights groups have blamed the disaster on an entrenched political class widely seen as inept.

Lebanon has a history of political assassinations, and authorities are now "entirely responsible for the judge's safety," the families warned.

Bitar, handling the biggest case since former prime minister Rafik Hariri's 2005 assassination, was forced to suspend his probe for 13 months after a barrage of lawsuits, mainly from politicians he had summoned on charges of negligence.

The judicial arm-wrestling between Bitar and Oueidat is the latest of crisis-torn Lebanon's mounting woes, as the value of the national currency hit new record lows against the US dollar this week.

On Wednesday, Human Rights Watch and Amnesty International called on the United Nations Human Rights Council to "urgently pass a resolution to create an impartial fact-finding mission" into the port explosion.

"The Lebanese authorities have repeatedly obstructed the domestic investigation into the explosion," the joint statement said.