The Observer's 20 photographs of the week

A riot police officer is engulfed by petrol bomb flames thrown by protesters during clashes in Athens. Greece's fragile coalition government faces its toughest test so far when lawmakers vote on new austerity measures demanded to keep the country afloat Photograph: Dimitri Messinis/AP

President Barack Obama celebrates with first lady Michelle Obama and their daughters Malia and Sasha at their election night victory rally in Chicago Photograph: Kevin Lamarque/Reuters

In Aleppo, a rebel fighter looks up towards the sky awaiting an attack by loyalists to President Bashar al-Assad Photograph: Narciso Contreras/AP

Gulls flock together while looking for food over St James's Park in London Photograph: Andy Rain/EPA

A woman tries to stop a bulldozer from destroying her house in Lenesia, south-west of Johannesburg. Protesters have burned tyres and blocked roads, after the government tore down houses built on plots that were illegally sold Photograph: AFP

Crosses displayed at the opening of a garden of remembrance in Princes Street Gardens in Edinburgh Photograph: David Cheskin/PA

An Indian girl is photographed through the broken window of a damaged car in a poor neighborhood of New Delhi, India Photograph: Kevin Frayer/AP

A bride waves at Pope Benedict XVI as he leaves Saint Peter's square at the Vatican Photograph: Tony Gentile/Reuters

A Palestinian woman, reflected in a mirror from furniture strewn outside her home, stands in front of the rubble of her house after it was demolished by Jerusalem municipality workers Photograph: Ahmad Gharabli/AFP

A child sleeps during Barack Obama's election night rally in Chicago Photograph: Kevin Lamarque/Reuters

Genetically engineered angelfish (Pterophyllum) glow in a tank at the 2012 Taiwan international aquarium expo. The fish are the world's first pink fluorescent angelfish and can view without black light Photograph: PICHI CHUANG/Reuters

Palestinians dance during a wedding ceremony in the Shati refugee camp in Gaza Photograph: Wissam Nassar/Corbis

A girl prepares lunch for her family on the beach in Kao Seng. Kao Seng is a traditional Muslim fishing village on the Gulf of Siam near the town of Songkhla Photograph: Jack Kurtz/Corbis

Naked volunteers perfom for artist Spencer Tunick in San Miguel de Allende. Tunick was in Mexico to produce an artwork commemorating the Day of the Dead Photograph: Alfredo Estrella/AFP

Li Rong sits on a bed in her cramped apartment on the fifth floor of an old industrial building in Hong Kong. Li lives in some of the priciest real estate per square foot in the world Photograph: Tyrone Siu/Reuters

Tiananmen Square is reflected in a glass door of the Great Hall of the People, where the opening ceremony of the 18th Communist party congress is being held Photograph: Alexander F Yuan/AP

The founder of a free school for slum children, Rajesh Kumar Sharma, checks the work of Somnath, an underprivileged Indian child, at a free school run under a metro bridge in New Delhi, India Photograph: Altaf Qadri/AP

Red deer hinds graze as the rutting season draws to a close in Glen Etive, Scotland. The rutting season sees the large red deer stags compete against each other for mating rights Photograph: Jeff J Mitchell/Getty

Students stand outside their classes at the Obama-Kogelo primary school a day before the US election. Barack Obama's father was born in Kogelo Photograph: Tony Karumba/AFP

Russian soldiers wearing Soviet second world war uniforms participate in the rehearsal of a military procession marking the anniversary of the parade of 1941, when soldiers left for the front line to fight German troops Photograph: Natalia Kolesnikova/AFP