The pan-European STOXX 600 index fell 0.7%, with the banking-heavy Spanish index down 2.2% and the French and Italian bourses more than 1% lower.

London's FTSE 100 slipped 0.7%, with British-Airways owner ICAG, easyJet and cruise operator Carnival down between 8% and 15% as talk of a second lockdown in the United Kingdom did the rounds after new COVID-19 cases almost doubled to 6,000 per day.

Travel and leisure was the worst-performing sector, down 3.5%.

Other European nations from Denmark to Greece announced new restrictions to curb surging coronavirus infections in some of their largest cities.

"If the uptick in cases becomes strong enough that lockdowns have to be tightened to a point that it derails the economic recovery, then it becomes a risk factor," said Mobeen Tahir, associate director of research at fund house Wisdom Tree.

The banking index <.SX7P> fell 2.6%, hitting its lowest level since May 26 and on course for record-lows as major central banks pledged to keep interest rates lower for a long time, with the Bank of England looking at taking borrowing costs to sub-zero levels, if needed.

Sparking hopes of consolidation among lenders battling the fallout from the COVID-19 pandemic, Caixabank agreed to buy state-owned Bankia for 4.3 billion euros ($5.10 billion) to create Spain's biggest domestic bank.

Bankia fell 4.8% and Caixabank was down 2.2% after rallying in the run up to the announcement.

Swedbank, SEB, Handelsbanken and Nordea were down between 1.8% and 5.3% on fears that the Swedish banks will bear the brunt of a recently proposed government "risk tax".

Separately, Sweden's financial watchdog said it was investigating Swedbank for potential market abuse.

The STOXX 600 still eked out 0.2% weekly gain as some major retail companies showed resilience in earnings earlier this week and a string of takeovers enlivened global M&A activity.

The London Stock Exchange Group entered exclusive talks to sell Borsa Italiana to France's Euronext, driving its shares up 4.3%.

Swedish telecoms gear maker Ericsson was up 1.3% after it agreed to buy U.S.-based wireless networking company Cradlepoint in a $1.1 billion deal.

(Reporting by Sruthi Shankar in Bengaluru; Editing by Saumyadeb Chakrabarty and Anil D'Silva and Kirsten Donovan)

By Sruthi Shankar