By Maya Gebeily

BEIRUT Lebanon on Friday mourned those killed in the port blast that devastated Beirut three years ago as religious leaders and rights groups decried the lack of accountability among political leaders who stymied the official investigation.

The explosion killed at least 220 people and wounded thousands more when hundreds of tonnes of ammonium nitrate stored in a warehouse detonated just after 6 p.m. (1600 GMT) on Aug. 4, 2020, sending a huge cloud over the city.

Despite the devastation, no senior figures have been held to account and an investigation has been obstructed by legal measures, prompting outrage in Lebanon and abroad.

Survivors and the families of victims say the lack of accountability has kept them stuck in 2020.

Rita Hitti lost her 26-year-old son, 34-year-old brother-in-law and 21-year-old nephew - all firefighters who responded to the call about a fire at the port on Aug. 4 and were killed when the blast went off.

"They were at the prime of their lives. Their lives were cut short - and we died along with them," she told Reuters.

Many shops and restaurants obliterated by the blast have been painstakingly rebuilt, hosting an influx of tourists and Lebanese expatriates late into Thursday night.

But on Friday, the usually-bustling streets were empty and businesses shuttered to mark a national day of mourning.

Rights group Amnesty International said it was unacceptable that no one has been held responsible for the tragedy.

"Instead, the authorities have used every tool at their disposal to shamelessly undermine and obstruct the domestic investigation to shield themselves from accountability - and perpetuate the culture of impunity in the country," said Aya Majzoub, Amnesty's deputy director for the region.

The explosion is thought to have been set off by a fire in a warehouse. The chemicals had been stored at the port since 2013 when they were unloaded during an unscheduled stop, but no one has claimed the shipment and it remained there despite senior officials knowing of its presence.

The probe, led by Judge Tarek Bitar, has been stalled since late 2021 by a slew of legal complaints filed against him by some of the suspects, including current and former officials.

In a memorial church service on the eve of the blast anniversary, Lebanon's top Christian cleric Patriarch Bechara Boutros al-Rai backed calls for an international fact-finding committee and called for a halt to meddling in the blast probe.

"What hurts these families and hurts us the most is the indifference of state officials who are preoccupied with their interests and cheap calculations," Rai said.

The blast hit as Lebanon was already struggling with a financial meltdown that began in 2019 and the COVID-19 pandemic. The economy has sunk further since, with the local currency losing 98% of its value and thousands of families impoverished.

(Reporting by Maya Gebeily; Editing by Angus McDowall and Angus MacSwan)