A large blast in the Lebanese capital, Beirut, has killed at least 70 people and injured more than 4,000 others, the health minister says.

Videos show smoke billowing from a fire, then a mushroom cloud following the blast at the city’s port. Officials are blaming highly explosive materials stored in a warehouse for six years, writes BBC.

President Michel Aoun tweeted it was “unacceptable” that 2,750 tonnes of ammonium nitrate was stored unsafely.

An investigation is under way to find the exact trigger for the explosion. Lebanon’s Supreme Defence Council said those responsible would face the “maximum punishment” possible.

Hospitals are said to be overwhelmed and many buildings have been destroyed.

President Aoun declared a three-day mourning period, and said the government would release 100 billion lira of emergency funds.