After years watching Tesla's electric cars speed ahead while they have been on the defensive over an industry-wide diesel emissions scandal, German high-end manufacturers have finally unveiled their first challengers to the Californian upstart.

Mercedes-Benz maker Daimler, BMW and Volkswagen's Audi and Porsche subsidiaries between them control some 80 percent of the worldwide premium car market.

But until recently they offered little battery-powered, zero-emission competition to Tesla and its bombastic chief executive Elon Musk. That changed this month, with all three groups unveiling their first all-electric SUVs slated for release over the next two years.

Audi rolled out its "E-Tron", BMW its "iNext" and Mercedes its "EQC", while Porsche presented an electric coupe, the "Mission E".

In total, German carmakers have vowed a total of almost 40 billion euros ($46.7 billion) of investment in battery-powered vehicles in the coming three years, industry association VDA says.

With a market share of around eight percent in Germany -- compared with Tesla's 0.1 percent -- Audi hopes electric cars will account for around one in three sales by 2025."Finally, it's getting started!" auto industry expert Ferdinand Dudenhoeffer told AFP.

Time is pressing, as sales of engines powered by automakers' longtime growth driver diesel have plummeted in the face of plans by many large cities to ban them to bring down air pollution.

The entrance of the three German behemoths into the electric race is far more consequential for Tesla than smaller fish like Britain's Jaguar, whose "I-PACE" is already on sale in the UK.

And the US tech firm faces major hurdles of its own, struggling to stem losses that have been going on for years while trying to reassure investors and customers of its chief executive's mental health.

Musk was filmed drinking whisky and smoking cannabis (which is legal in California) with radio host Joe Rogan earlier this month, and in August revealed he was suffering from intense stress and fatigue in an interview with the New York Times.

On Tuesday, Tesla confirmed that the US Department of Justice was investigating the company over Musk's tweet announcing a plan to remove its shares from the stock market.

Also on Twitter, the South African entrepreneur admitted Tuesday that after months spent overcoming "production hell" on the firm's mass-market Model 3, it was now in "delivery logistics hell" struggling to get cars to buyers -- while promising "rapid progress".