The Observer's 20 photographs of the week

As temperatures approach 40C, people head to the water and crowd an artificial wave pool in Daying, China Photograph: China Daily/Reuters

At Copacabana beach in Rio, two Polish nuns get their feet wet. Hundreds of thousands of young Catholic pilgrims started gathering for a prayer vigil with Pope Francis Photograph: Yasuyoshi Chiba/AFP

A shovel sits in oil-covered sand at Ao Phrao beach. Volunteers were attempting to clean up the area after a major oil slick hit the island of Ko Samet, Thailand. Environmentalists accused a Thai energy firm of understating the extent of the pipeline leak Photograph: Nicolas Asfouri/AFP

Photographer Nacho Doce was covering the unrest in Sao Paulo. Here he captures the confrontation between military police and demonstrators from the 'Black Bloc' group during a protest against State Governor Geraldo Alckmin Photograph: Nacho Doce/Reuters

And in this photograph by Nacho Doce, a Black Bloc demonstrator is detained by the military police Photograph: Nacho Doce/Reuters

At Chester Zoo, a Sumatran tiger cub reacts as it is lifted by veterinary staff during a health check Photograph: Phil Noble/Reuters

Photographers had access to North Korea for the 60th anniversary commemorations of the truce in the Korean War. Here Ed Jones photographs workers tending to the grass at the Kumsusan Palace in Pyongyang Photograph: Ed Jones/AFP

In another accomplished photograph by Ed Jones, North Korean soldiers leave their seats following a performance celebrating the 60th anniversary of 'victory in the great Fatherland Liberation War' at the Ryugyong Jong Ju Yong Indoor Stadium in Pyongyang Photograph: Ed Jones/AFP

Reuters photographer Jason Lee was also in Pyongyang, here adroitly capturing thousands of North Koreans at a commemoration event at the Kim Il-Sung Stadium in Pyongyang Photograph: Jason Lee/Reuters

US Army Private First Class Bradley Manning is escorted by military police as arrives to hear the verdict in his military trial at Fort George G Meade, Maryland. Manning was convicted of espionage and faces a lengthy jail term despite being cleared on the most serious charge of 'aiding the enemy' Photograph: Mark Wilson/Getty

People look at a section of the 360 degree panoramic picture of the historic Battle of the Nations in Leipzig. The monumental picture created by Yadegar Asisi displays scenes from the 1813 battle between Napoleon's retreating army and troops from Austria, Prussia, Russia and Sweden Photograph: Thomas Peter/Reuters

Mammatus clouds move over the Fredericksburg Agricultural Fair in Virginia, US, after thunderstorms had passed through the area. Mammatus are most often associated with severe thunderstorms Photograph: Peter Cihelka/AP

Umbrellas provide shade for pedestrians in Getafe, on the outskirts of Madrid Photograph: Juan Medina/Reuters

Tom Jenkins skillfully captures Usain Bolt in dramatic close-up after running in the 4x100m relay during the Anniversary Games at the Olympic Stadium in London
Photograph: Tom Jenkins/The Guardian

Participants dive in the pool at the start of a heat in the women's 200m freestyle in the FINA World Championships at Palau Sant Jordi in Barcelona Photograph: Francois Xavier Marit/AFP

The Czech Republic's Michal Navratil performs an exhibition dive dressed as Superman at the end of the men's 27m high diving final in Barcelona Photograph: Gustau Nacarino/Reuters

Joe Penney continues his excellent work in Mali with this photograph of a woman carrying her baby through a sandstorm in Timbuktu Photograph: Joe Penney/Reuters

Rescuers prepare the coffins of victims of a bus crash on the road between Monteforte Irpino and Baiano, Italy. At least 36 people were killed and several more injured after a coach carrying pilgrims plunged off a motorway flyover Photograph: AFP

An aerial view of the destruction in the Khalidiya district of Homs. Syrian troops drove insurgents from the central district of Homs this week, tightening their siege on remaining rebel bastions in the city, which links Damascus to the Mediterranean heartland of President Bashar al-Assad's Alawite sect Photograph: Reuters

And inside Homs, photographer Joseph Eid captures Syrian government soldiers driving a tank through a devastated street in the Khalidiya district Photograph: Joseph Eid/AFP