Alarmed Casablanca residents fled their homes and stayed in the streets
The epicentre was in the High Atlas Mountains, 71km (44 miles) south-west of Marrakesh, at a depth of 18.5km, the US Geological Survey said.
The quake struck at 23:11 local time (22:11 GMT). There was a 4.9 aftershock 19 minutes later.
People died in Marrakesh and several areas to the south, the ministry said.
"According to a provisional report, the earthquake killed 296 people in the provinces and municipalities of al-Haouz, Marrakesh, Ouarzazate, Azilal, Chichaoua and Taroudant," the statement said, adding that 153 people were injured and hospitalised.
Unverified video clips on X (formerly Twitter) show damaged buildings, other buildings shaking and rubble-strewn streets. People are seen fleeing in alarm and some walking through clouds of dust.
Some buildings in Marrakesh's old city have collapsed, one resident told the Reuters news agency. Several clips on X show buildings crashing down, but the BBC has not identified where they were.
Locals are said to have decided to stay outside their homes in case the city is rocked by powerful aftershocks.
Another man in the historic city described feeling a "violent tremor" and seeing "buildings moving".
"People were all in shock and panic. The children were crying and the parents were distraught," Abdelhak El Amrani told the AFP agency.
He said power and phone lines were down for ten minutes.
AFP also reported that one family was trapped in the collapsed rubble of a house - and that a number of people in the city were taken to hospital.
The quake's epicentre in a remote area of the High Atlas Mountains was relatively shallow - and tremors were also reportedly felt in the capital Rabat, some 350km away, as well as Casablanca and Essaouira.
Simple buildings in mountain villages near the epicentre may not have survived and, being remote, it may take some time to determine casualties there.
-- Courtesy of BBC News
