New Year celebrations marred by widespread protests and wildfires as world welcomes 2020

Mass unrest in opposition to Narendra Modi’s citizenship law as India rang in new decade

The world has welcomed 2020 with a mixture of excitement and caution, as the new year is marked by protests and reflection.

Wildfires, widespread protests and sickness marred celebrations and many countries used the new year as an opportunity to put difficulties behind them as well as to look forward into the future.

In the UK, London mayor Sadiq Khan promised that the traditional fireworks would be better than any the city had ever seen. At midnight, a 10-minute extravaganza lit up the London Eye, accompanied by music from the Lightning Seeds, Stormzy and others.

Prime Minister Boris Johnson promised to push forward with Brexit and bring the country together in a New Year's address to the country.

In many nations, the celebration of the arrival of 2020 came with protests that looked to draw attention to ongoing political struggles.

Amid unrest that has run throughout 2019, and which protesters promised would continue into 2020, Hong Kong opted to cancel the famous fireworks show that traditionally lights up Victoria Harbour amid safety concerns. Instead, authorities laid on a light show.

Demonstrators nonetheless committed to disrupt the celebrations, and police used roadblocks and rough tactics to keep people from causing disruption to the city's nightlife and New Year's Eve celebrations.

India's celebrations also saw considerable protests as opposition continues against a citizenship law that activists say will discriminate against Muslims and undermine India's secular constitution. Thousands of protestors took to the streets in cities like New Delhi, which is being hit by one of its coldest winters in recorded history.

In other countries, the excitement of the new year was met with sombre reflection on the year that had passed. Countries from New Zealand to Russia used the opportunity to reflect on the troubles of the previous years and leaders broadcast messages urging people to come together.

In Samoa – the first country to see in the new decade – the traditional fireworks came amid reflections on a measles epidemic that swept across the country's small population in recent months, killing 81 people, many of whom were very young children.

Australia saw more than 1 million people arrive in Sydney Harbour, hazy from the wildfires that have ravaged the surrounding countryside. There had been a suggestion that the famous fireworks show should be cancelled this year, to allow more time and resources to deal with the ongoing fires – and in other parts of Australia, fireworks shows did not go ahead – but the capital hosted a dazzling firework display that saw more than 100,000 explosions.

Even as that display happened, some Australians were forced onto the beaches to flee from the bushfires that have spread through the country.

At New York's six-hour celebration, the 60-second ball drop in Times Square was due to begin with a button pressed by high school teachers and students, there to spotlight climate change and the effort to fight it.

In the UK, New Year's Eve brought its own reminder of the changing climate, with the Met Office announcing that it had recorded the hottest December day ever. The year had seen a range of extreme weather in Britain, as the hottest winter day and hottest day ever were both recorded in 2019.