Deutsche Bank has begun the process of culling 18,000 staff worldwide, with members of its 8,000-strong UK workforce among those facing the axe.
The German lender is scaling back its investment banking division – which has its biggest centre in London – as part of the plans to cut a fifth of its global headcount.
Chief executive Christian Sewing declined to give a breakdown of where the jobs axe would fall, but insisted that London would remain a “critical part” of its plans.
Staff in Sydney, Hong Kong and elsewhere in Asia were the first to learn that they were set to lose their jobs, as the global working day began.
Later, an IT worker in London told the Reuters news agency: “I was terminated this morning. There was a very quick meeting and that was it.”
Investors initially cheered the restructuring, sending shares 3% higher in early trading. But sentiment later turned sour and the stock was more than 5% down by the close of trading.
Mr Sewing said the “deep cuts” would not be focused on one region, but there was speculation that Europe and the US would be worst affected.
Deutsche Bank employs about 7,000 people in London, which is home to its largest investment banking operations in the world, with other UK staff based in Bournemouth and Birmingham.
In a statement on its future in the UK, the bank added: “We will retain a significant presence here and remain a close partner to our UK clients and to international institutions that want to access the London market.
“We regret that the changes we are making will affect some of our colleagues and we will do everything we can to support them.”
Mr Sewing said plans for a new City HQ would not be affected by the shake-up.
In a letter to Deutsche’s global workforce, Mr Sewing said: “I personally greatly regret the impact this will have on some of you.
“In the long-term interests of our bank, however, we have no choice other than to approach this transformation decisively.”
Deutsche’s restructuring plan will cost it €7.4bn (£6.6bn) and is expected to send it to a second-quarter financial loss of €2.8bn (£2.5bn).
The lender’s share price has collapsed in recent years after its investment banking arm – once the focus of ambitious expansion plans – faltered.
Now, it is moving away from the aim of taking on Wall Street’s giants, scrapping its global equities business and cutting some operations in its fixed income division.
Instead it will place more focus on its core corporate banking business, reining in a strategy under which, Mr Sewing said, it was “spread too thin”.
He said the bank was now going further than previous attempts at “trimming” itself, instead axing whole businesses within the group.
Analysts at JP Morgan called the plan “bold and for the first time not half-baked” but said questions remained about its execution.