LONDON (Reuters) – Aid organizations laid out 2,500 lifejackets symbolizing refugee crossings to Europe in a demonstration outside the British parliament on Monday timed to coincide with a United Nations summit on the worldwide migrant crisis.

The orange lifejackets spread out on the lawn of Parliament Square were worn by adults and children traveling from Turkey to Greece, part of a wave of migrants attempting the Mediterranean crossing to get to mainland Europe.

The United Nations refugee body UNHCR, International Rescue Committee, Migrant Voice, World Vision, and Médecins Sans Frontières collaborated for the display, which they called a “lifejacket graveyard” to illustrate the risks migrants take.

The UNHCR estimates 6,940 people drowned or went missing while trying to reach Europe between January 2015 and August 2016.

A display of lifejackets worn by refugees during their crossing from Turkey to the Greek island of Chois, are seen Parliament Square in central London, Britain September 19, 2016. REUTERS/Stefan Wermuth

“We hope this will send a message to the world leaders to call for durable solutions,” said Sanj Srikanthan, head of policy and practice at International Rescue Committee.

In New York, leaders of 193 states were gathering for the United Nations General Assembly, which was opening with its first ever summit specifically addressing global movements of refugees and migrants.

Aid organizations have often called on Britain to take more refugees but Prime Minister Theresa May was preparing to defend her country’s record.

She was expected to affirm the right of all countries to control their borders, a government statement said, and would call for “reducing unmanaged population movement” along with measures to help refugees claim asylum in the first safe countries they reach.

(Reporting by Helen Reid; editing by Stephen Addison)