The conclave being held in the Vatican to elect a new Pope has failed to select a successor to Pope Francis, as black smoke rises from the Sistine Chapel chimney. Traditionally if a new Pope is elected then white smoke would have been emitted from the stack.

A group of 133 cardinal electors began their behind-closed-doors meeting on Wednesday afternoon. It is expected voting will resume on Thursday, and up to four rounds of voting can take place each day - two in the morning and two in the afternoon.

Cardinals, mostly dressed in distinctive bright red vestments, heard at a special mass on Wednesday of the "choice of exceptional importance" they must make in electing the 267th pope. A new pope requires a two-thirds majority in the voting, and white smoke will be emitted from the specially erected chimney of the Sistine Chapel to confirm a pontiff has been chosen.

There are three UK cardinals taking part in the conclave, Cardinal Vincent Nichols, Cardinal Timothy Radcliffe and Rome-based Cardinal Arthur Roche.

Cardinal Kevin Farrell, who is Irish-born, is seen as an American cardinal having ministered mainly in the US.

Cardinal Nichols had called on people to pray for himself and other cardinals as they embark on the secret voting process, adding that he feels "quite intimidated" knowing the world is watching to see who they choose.

The voting cardinals, those aged under 80 who are the only ones eligible to cast a ballot, were urged to "invoke the help of the Holy Spirit" to help them elect a pope "whom the (Catholic) Church and humanity need at this difficult and complex turning point in history".

Addressing them in St Peter's Basilica, Cardinal Giovanni Battista Re said: "To pray, by invoking the Holy Spirit, is the only right and proper attitude to take as the cardinal electors prepare to undertake an act of the highest human and ecclesial responsibility and to make a choice of exceptional importance.

"This is a human act for which every personal consideration must be set aside, keeping in mind and heart only the God of Jesus Christ and the good of the Church and of humanity."

The pontiff - believed to be someone called to be the successor to St Peter, who was the first pope - will need to be a person who can "awaken the consciences of all and the moral and spiritual energies in today's society, characterised by great technological progress but which tends to forget God", Cardinal Battista Re added.

Following a centuries-old tradition, cardinals are cut off from all communications with the outside world while they take part in the anonymous voting process.

In a livestream from the Sistine Chapel, the electors could each be seen taking an oath pledging secrecy on their vote and what happens at conclave.

At around 4.45pm UK time, a Vatican official declared "extra omnes", the Latin phrase telling non-cardinals to leave, with the large brown doors of the chapel shut shortly after.

The livestream cut to crowds in St Peter's Square in front of St Peter's Basilica, some of whom waved when they spotted they were on camera.

This conclave is thought to be one of the most diverse of any meeting of cardinals before, representing some 70 countries and hailing from places such as Mongolia, Sweden and Tonga which had not had a cardinal before.

Pope Francis had appointed some 108 of the 133 cardinals who will choose his successor.

The next pope must be someone who can bring together disparate groups within the Catholic Church, an emeritus professor of Catholic theology at the University of Bristol said.

Professor Gavin D'Costa said: "This conclave is more universal in representative terms than any other in the history of the Church, even if it is also lacking in balance - having more European cardinals than any other single group, but with a dwindling Catholic population in Europe.

"The priority will be to select a pope who embodies the common good, who can unite disparate groups within Catholics, and provide a vision of the Church that can be conducive to peace, co-operation and justice in a broken world."

Francis was vocal on politics, speaking out against war and climate change, as he urged more focus on the poor and downtrodden of the world.

His funeral last month drew hundreds of thousands of mourners, including world leaders such as US President Donald Trump and UK Prime Minister Sir Keir Starmer.

Such was Francis's popularity, he was dubbed by many to have been "the people's pope".