BEIRUT: Lebanon's lead investigator into the catastrophic Beirut port explosion charged outgoing premier Hassan Diab and three ex-ministers with negligence on Thursday, a judicial source said. They are the first politicians to be indicted over the devastating August 4 blast that killed more than 200 people, disfigured the heart of the capital and stoked a wave of public anger against Lebanon's ruling elite.

The four were charged with "negligence and causing death to hundreds and injuries to thousands more" in the first such official indictment against a prime minister in office in Lebanese history, the judicial source said. After the blast, it emerged top security officials and politicians had known for years about hundreds of tonnes of ammonium nitrate fertiliser stored haphazardly at the Beirut port but had failed to take precautionary measures.

The decision by judge Fadi Sawan came after the investigation confirmed the suspects had received "several written notices warning them against postponing the disposal of ammonium nitrate fertiliser," the source said.

The other senior officials charged are former finance minister Ali Hasan Khalil and the ex-ministers of public works Yusef Fenianos and Ghazi Zaiter. The United States in September slapped sanctions on Khalil and Fenianos for alleged corruption and support of the powerful Hezbollah movement.