People wave flags as the naval guided missile frigate Yuncheng (571) arrives at the Ngong Shuen Chau Naval Base in Hong Kong.  The frigate is open to the public as part of events celebrating the 15th anniversary of Hong Kong's handover to China. (Reuters)

Ken Livingstone, Britain's Labour candidate for London mayor, stands in front of a poster depicting London Mayor Boris Johnson as an alien, to launch Labour's new Ad Bus in south London. (Reuters)

People walk along the OCBC Skyway linking the Supertrees, that range from 25-50 meters in height and serve as vertical gardens, in an area near Singapore’s busy financial district. The city-state is making efforts to nurture greenery and capture the essence of Singapore as a tropical city. (AP)

A man passes images of jailed opposition leaders on a wall in Barbar, Bahrain, west of Manama. Political leaders pictured from left are: Hassan Mushaima, Sheik Mohammed Habib Moqdad, and Abdulwahab Hussein. (AP)

An Afghan policeman destroys an opium poppy field in Alingar, Laghman province, east of Kabul. A bomb exploded next to the fields during an eradication campaign in Alingar, wounding two police officers. Afghanistan supplies most of the world's opium. (AP)

Women display their palms that are painted in the colors of the Yemeni flag and the Syrian revolutionary flag during a demonstration calling for Yemen's former President Ali Abdullah Saleh to be put on trial in Sanaa. (Reuters)

Queen Beatrix of the Netherlands walks in a ticker tape parade during the annual traditional Queens' Day in Veenendaal. (Reuters)

Pupils attend a class at El Mana islamique at Bori Bana, a slum in Abidjan, Ivory Coast.  The school, which teaches French and Arabic, houses about 200 pupils in three classrooms. The school fee for each pupil costs about $50 per year. (Reuters)

Roger Lewis, with the Treme Brass Band, performs at a sunrise concert marking International Jazz Day at Congo Square in New Orleans. Thousands across the globe are expected to participate in celebrations, including events in Belgium, France, Brazil, Algeria and Russia. (AP)

Horses enter and leave the race track in the early morning at Churchill Downs in Louisville, Kentucky. The historic track will host the 138th Kentucky Derby on Saturday. (AP)

A man uses a machine to harvest tulips in a field in the northern German city of Schwaneberg. (AFP)

Laborers have lunch at a construction site in Sidon, southern Lebanon, ahead of May Day. (Reuters)

French shoe designer Christian Louboutin opens his first-ever retrospective exhibition at the Design Museum in London. The exhibit showcases how Louboutin has helped transform the design of the shoe over the past 20 years. (AP)