European stock markets slipped on Tuesday as a rebound in the previous session fizzled out, with investors remaining cautious ahead of the first US presidential debate.

The pan-European STOXX 600 was down 0.5pc after recording its biggest single-day gain in three months on Monday.

Banks handed back some of the previous session's 5.6pc gain, while insurers and automakers fell nearly 1pc as the global death toll from the COVID-19 pandemic crossed 1 million, according to a Reuters tally.

While there were some signs of progress in talks over a fresh US coronavirus relief bill, investors were mostly in a wait-and-see mode as US Democratic presidential nominee Joe Biden and President Donald Trump looked set to square off in their first debate in Cleveland, five weeks before the election.

"Even a half decent performance from Joe Biden could well trigger some anxiety in US equity markets given that the Democrats have a much more interventionist stance towards business and the economy," Michael Hewson, chief market analyst at CMC Markets wrote in a note.

"This may help explain the more cautious tone for markets in Europe today, particularly as we are coming to the end of the month, as well as the quarter."

While Monday's bounce back helped the STOXX 600 turn positive for the third quarter, the benchmark was on course to end September with a more than 1pc drop, its biggest since the peak market selloff in March, amid concerns of a second wave of COVID-19 infections, Brexit developments and the upcoming US election.

Among individual movers, Air France KLM fell 4.0pc after HSBC downgraded the stock to "reduce" from "hold".

British plumbing parts distributor Ferguson jumped 4.8pc as it restored its dividend after a series of cost-reduction measures and resilience in its main US business helped it report a 4.1pc rise in annual profit.

British baker Greggs slipped 3pc as it cautioned that the outlook was uncertain because of the pandemic and it would have to cut staff jobs and hours.