Leaving concerns over the implications of the mounting debt crisis behind them, Europeans welcomed 2012 in style.

Big crowds gathered in almost all major cities in the continent to celebrate the arrival of 2012. In London, tens of thousands of revellers witnessed the events, especially fireworks over the Thames. Moscow's Red Square, Berlin's Brandenburg Gate, Spain's Madrid city all witnessed huge crowds.

But Europe's leaders urged the people to remain cautious in view of the debt crisis, in their New Year greetings. The somber tone was evident in the message of German Chancellor Angela Merkel who warned that 2012 would be tougher than 2011.

French President Nicolas Sarkozy too shared the same view. "What is happening in the world announces that 2012 will be a year full of risks but also full of possibilities. We have to be courageous and we have to be lucid," Sarkozy said in a televised message to the nation. Greek Prime Minister Lucas Papademos too warned of a difficult year.

Here are some of the moments of New Year celebrations across Europe:

Fireworks explode in the sky over Bucharest, Romania, at midnight, Sunday, Jan. 1, 2012, during street celebrations of the new year. Large crowds gathered downtown Romania's capital taking advantage of the dry weather to attend the celebrations.PA
Tar Barrels are lit in readiness for the traditional Allendale New Year Tar Barrel Parade in Allendale, Northumberland, to mark the New Year.PA
Fireworks over Edinburgh Castle during celebrations to mark the new year at the Hogmanay street party, Edinburgh.PA
Fireworks over the London Eye, in central London, as part of the New Year celebrations.PA
Fireworks light the sky above the Quadriga at the Brandenburg Gate in Berlin shortly after midnight, greeting the New Year.PA
Fireworks explode over the Houses of Parliament, including St. Stephen's Tower, which holds the bell known as Big Ben, as London celebrates the arrival of New Year' on Sunday.PA
Russians celebrate the New Year on Red Square in Moscow, with the Kremlin in the background, right, and St. Basil's cathedral in background left, Russia, Sunday, Jan. 1, 2012. Tens of thousands of people gathered on the Square to celebrate the new year, and view the fireworks as the clock on the Kremlin's Spassky Tower, right, struck midnight.PA
Fireworks light the sky above the Cathedral Square in Vilnius shortly after midnight, greeting the New Year, Sunday, Jan. 1, 2012. Thousands of people celebrated the beginning of the New Year 2009 in the Lithuanian capital.PA
Fireworks explode over the ancient Acropolis Hill with the Parthenon temple during the New Year's celebrations in Athens.PA
Fireworks explode over the London Eye in central London as part of the city's New Year celebrations on Sunday.PA