European markets closed slightly lower on Tuesday as traders monitored geopolitical developments on both sides of the Atlantic.

The pan-European Stoxx 600 ended the session just below the flatline, with travel and leisure stocks adding 1% to lead gains.

Stocks in the sector rallied on Tuesday on the back of British travel firm Thomas Cook's collapse a day earlier, with the U.K.’s Tui gaining 6.5% to surge to the top of the index.

Markets were also largely attuned to political developments.

In a landmark case on Tuesday, the U.K.'s highest court ruled that Prime Minister Boris Johnson’s suspension of parliament for five weeks until October 14 was unlawful. Sterling traded 0.3% higher at around $1.2466 on the back of the news, while the FTSE 100 shed nearly 0.5%.

Source: CNBC