Channel 4's multi-award-winning foreign affairs strand returns for a new series with a film following a volunteer ambulance service in Somalia's war-torn capital, Mogadishu. Reporter Seyi Rhodes and director Sasha Achilli accompany the extraordinary team who risk their lives braving bombs, gunfights and al-Shabaab militants to get sick people to hospital in a city where the government struggles to cope and where they are many people's only hope.

Reporter Marcel Theroux and director Kate Hardie-Buckley travel to Mongolia's capital Ulaanbaatar, where the air quality can reach more than 100 times the accepted limit and is causing a public health disaster. A layer of smog caused by coal smoke blankets the city. The smog is full of floating soot particles, some of which are small enough to bypass the body's defences, causing fatal illnesses including respiratory disease, heart disease and cancer. According to Unicef, cases of respiratory infections have tripled here over the last 10 years as pollution surges. The team visit a children's hospital where senior paediatrician Dr Oyenbileg tells Theroux that respiratory illness is the biggest killer of children under five, as they are more susceptible to respiratory diseases such as bronchitis and pneumonia.

Reporter Rania Abouzeid and director Karim Shah travel to Kabul where the population, long used to living with bombs and gunfights, face a new danger: criminal gangs who kidnap for ransom. Often their victims are children. The Unreported World team join the lead detective of the police anti-kidnap squad as they attempt to reunite kidnap victims with their families.

Krishnan Guru-Murthy visits Caribbean tourist destination the Dominican Republic, to investigate terrible crimes being committed against teenagers by sex tourists.

Unreported World investigates how the #MeToo campaign has taken off in India's film industry, meeting top actresses who are speaking out against assault, sexual harassment and rape.

As the Brazilian army assists the police in tackling drugs gangs in Rio de Janiero, Ade Adepitan joins young journalists reporting from inside one of the cities most violent favelas.

Krishnan Guru-Murthy visits Colombia to investigate the plight of some of the one million children fleeing poverty, hunger and medical shortages in Venezuela.

Unreported World goes undercover with a private detective agency in Delhi owned by a woman. The explosion in online dating and matchmaking apps in India has led to a huge rise in the number of private investigators tasked with exposing love cheats or checking out a fiance's suitability. However, as reporter Nelufar Hedayat and director Charlie Mole discover, some agencies are using questionable tactics in their attempts to uncover the truth.

Marcel Theroux travels to North Korea at a time of great change for the secretive nation and takes a tour around some of the sights and witnesses the Mass Games celebrating the DPRK's 70th birthday.

This documentary series offering the lowdown on hard-hitting issues from around the globe continues. Here, reporter Seyi Rhodes and director Eric McFarland visit Johannesburg to meet miners who are risking their lives to descend deep underground in South Africa's abandoned gold mines, hoping to scratch a dangerous living from whatever ore remains. With the mines controlled by violent gangs and surrounded by lawless settlements, the pair's miniature cameras capture the stark reality of life at the end of a gold rush.

Krishnan Guru-Murthy travels to El Salvador to reveal what life is like for deportees from the US who are sent back to the gang-ravaged country following Donald Trump's crackdown on illegal immigration. President Trump says his government's latest crackdown is aimed at removing criminals and illegal immigrants, in particular members of the notorious Salvadoran-American street gang MS-13. However, official figures show that an increasing number of those who are being deported have no criminal record.

Sahar Zand reports from Mauritania in West Africa, where young girls and women are being force fed up to 10,000 calories a day because, when it comes to marriage, big is deemed beautiful.