The Observer's 20 photographs of the week

Photographer Ben Curtis produced powerful work this week from the humanitarian crisis in South Sudan. Here, a displaced family, one of the few to have a mosquito net, wake up under it after fleeing the recent fighting between government and rebel forces in Bor by boat across the White Nile Photograph: Ben Curtis/AP

And here, displaced people prepare to sleep in the open at night in the town of Awerial, South Sudan Photograph: Ben Curtis/AP

US Marines hold an American flag at the Holiday Bowl National Collegiate Athletic Association (NCAA) college football game in San Diego Photograph: Gregory Bull/AP

People celebrate the New Year at Copacabana beach in Rio de Janeiro, Brazil Photograph: Yasuyoshi Chiba/AFP

Palestinians wave their national flag as they await the release of prisoners to Jerusalem. Israel has freed 26 Palestinian prisoners under peace talks brokered by the US secretary of state John Kerry, who is returning to the region to boost the faltering negotiations Photograph: Menahem Kahana/AFP

This vivid image of Rafael Nadal playing Novak Djokovic in London was taken back in November but I have put it in this week's 20 as Tom Jenkins has included it in a gallery of his best sports photos of 2013 in which he describes the story behind each image
Photograph: Tom Jenkins/The Guardian

Goalkeeper Petr Cech of Chelsea grasps at the ball as Martin Skrtel of Liverpool scores the opening goal at Stamford Bridge in London Photograph: Clive Rose/Getty

Flood waters remain on the racecourse in Tonbridge, Kent, as more heavy rain swept across the UK Photograph: Gareth Fuller/PA

Jockey Sam Twiston-Davies returns after pulling up on Pigeon Island at Cheltenham racecourse Photograph: Alan Crowhurst/Getty

An activist participates in a rally to mark the 105th year since the birth of Stepan Bandera, one of the founders of the Organisation of Ukrainian Nationalists, in Kiev Photograph: Reuters

A pro-European demonstrator holds a mirror which reflects a group of riot police officers standing guard in Kiev, Ukraine. Opposition activists have now protested for over a month opposing the government's decision to shelve a key deal with the EU Photograph: Sergei Chuzavkov/AP

Dale De La Rey photographed residential estates in Hong Kong after a recent report which concluded that Hong Kong's house prices are the world's highest Photograph: Dale De La Rey/AFP

An Indian child is seen in a temporary shelter during a cold winter morning at the old quarters of Delhi, India. The winter takes a heavy toll each year as poverty forces many homeless people to live outdoors Photograph: Money Sharma/EPA

Balinese girls in traditional costumes gather during a parade for this year's last sundown in Bali island, Indonesia, on New Year's Eve Photograph: Firdia Lisnawati/AP

A massive fireball from an oil-laden train rises into the air just west of Casselton, North Dakota. A freight train derailed and was hit by a 106-car oil train. No injuries were reported Photograph: Dave Arntson/Corbis

Photographer Andreea Campeanu has been in the Central African Republic, producing strong and poignant images from the aftermath of the violence there. Here, a woman looks at burning houses as the fighting continues between Muslim Seleka rebels, who seized power in March, and Christian self-defence militia Photograph: Andreea Campeanu/Reuters

And here, at the Complex Paediatric Hospital in Bangui, she photographs a boy in a wheelchair who sustained wounds from a grenade attack Photograph: Andreea Campeanu/Reuters

A Lebanese man carries an injured woman away from the site of a car bomb explosion in a Shia area and stronghold of the Lebanese militant group Hezbollah in Beirut Photograph: Hussein Malla/AP

A freediver swims beside a sperm whale off the coast of Dominica in the Caribbean Photograph: Franco Banfi/Barcroft

Supporters of the ruling Bangladesh Awami League beat a lawyer and supporter of the main opposition Bangladesh Nationalist Party during a protest by opposition activists in Dhaka, Bangladesh Photograph: A M Ahad/AP