The London Stock Exchange witnessed a rise of more than 1.5 percent Monday, the first trading day since Britain officially left the single market and the European Union's customs union.

The benchmark FTSE 100 index rose 1.54 percent and reached 6,560.33 points at opening after New Year's Eve lost 1.5 percent when it was last traded.

In the euro zone Monday, the DAX 30 index in Frankfurt rose 1.2 percent, and so did the CAC 40 index in Paris, up 1.3 percent.

The United Kingdom formally left the European Union Jan. 31, 2020, but remained in a transition period until Dec. 31 2020, while the two sides were negotiating a post-Brexit trade agreement that concluded Dec. 24.

Britain formally left the European Customs Union and the single market at 23:00 GMT Dec. 31.

"The actual effects of the UK's exit from the European Union are still unknown, but reaching a trade agreement before the deadline removes some of the burden that has been haunting the index for some time," said Richard Hunter, head of markets at Interactive Investor.

Asian stock markets recorded a strong start to the year, with increasing optimism about the economic outlook, despite persistent concerns about the health crisis resulting from COVID-19.

Investors hope that introducing vaccines against the virus will stem the rise in infection rates.