The continent's bourses trimmed their morning losses, and the pan-European STOXX 600 ended the day 0.1% lower while euro zone stocks slipped 0.3%.

A messy face-off between U.S. President Donald Trump and Democratic rival Joe Biden overnight kept risk assets under pressure earlier in the day as Trump cast doubt on whether he would accept the election outcome if he lost.

But Wall Street mood improved, with the main indexes jumping more than 1% after U.S. officials expressed hope for a breakthrough on a COVID-19 relief package.

"After a slow start, U.S. indices have moved firmly into positive territory. This has dragged Europe out of the red too," wrote IG's Chris Beauchamp.

The STOXX 600 closed out a volatile third quarter nearly flat, and posted a 1.5% decline for September as worries about a second wave of COVID-19 infections hampering Europe's economic recovery and doubts about a Brexit trade deal came to the fore.

Britain reported more than 7,000 COVID-19 cases for the second day in a row, and several European countries looked at tightening restrictions in an effort to contain the spread of the virus over autumn and winter.

A handful of M&A activity drove big moves, with TP ICAP, the world's biggest inter-dealer broker, slumping 16.4% to the bottom of STOXX 600 after saying that it was in talks to buy electronic trading network Liquidnet Holdings for $600 million to $700 million.

Dutch specialty chemicals company DSM rose 4% after Germany's Covestro said it would buy its resins and functional materials unit for about 1.6 billion euros ($1.88 billion). Covestro slid 7%.

French waste and water management company Suez SA jumped 5.9% after bigger rival Veolia raised its offer to buy a stake in the company.

Oil major Total gave the biggest boost to the markets, rising 3.1% after saying it would hike its annual investments in renewable energy and electricity by 50% amid gloomy long-term prospects for oil demand.

Another energy player Royal Dutch Shell slipped 1.3% after announcing plans to cut over 10% of its workforce.

The broader oil & gas index, among the worst performers in Europe alongside banks <.SX7P> this year, rose 0.9%.

By Sruthi Shankar