The United Nations paid tribute Wednesday to humanitarian workers now battling the COVID-19 pandemic after a year in which they found themselves under greater attack than ever before.

The UN marked its World Humanitarian Day by remembering the 125 aid workers who were killed in 2019 and the hundreds of others who were wounded or kidnapped.

UN human rights chief Michelle Bachelet took part in a wreath-laying ceremony at the United Nations in Geneva.

"Let's never forget their love for humanity that led them to the ultimate sacrifice: their lives," she said.

According to the Aid Worker Security Database compiled by the Humanitarian Outcomes research group, major attacks against humanitarians last year surpassed all previous years since records began in 1997.

In 277 separate incidents around the world, a total of 483 relief workers were attacked, of whom 125 were killed, 234 wounded and 124 kidnapped.

The figure represents an 18-percent increase in the number of victims compared to 2018.

Most of the attacks occurred in Syria, followed by South Sudan, the Democratic Republic of the Congo, Afghanistan and the Central African Republic.

OCHA, the UN Office for the Coordination of Humanitarian Affairs, said each attack was a tragedy for those targeted, but also for the thousands of vulnerable people they were trying to assist.

"The UN condemns these attacks, and it calls for accountability for perpetrators and justice for survivors. Relief workers cannot be a target," said OCHA.

UN human rights chief Michelle Bachelet, left, at a Geneva wreath-laying ceremony marking World Humanitarian Day
UN human rights chief Michelle Bachelet, left, at a Geneva wreath-laying ceremony marking World Humanitarian Day AFP / Fabrice COFFRINI

The UN said aid workers and healthcare responders were now going to extraordinary lengths to help people whose lives have been upended by crises -- and now by the global COVID-19 pandemic.

"This year, humanitarian workers are stretched like never before," UN Secretary-General Antonio Guterres said in a statement.

"They are responding to the global crisis of COVID-19, and with it the massive increase in humanitarian needs from the fallout of the pandemic.

"They are the unsung heroes of the pandemic response -- and they all too often risk their own lives to save the lives of others."

On Tuesday, the Red Cross said more than 600 attacks on health workers and patients had been reported in connection with the COVID-19 crisis.

The ceremony in Geneva also remembered seven aid workers with French non-governmental organisation ACTED who were killed at a wildlife haven in Niger on August 9.

Luca Pupulin, who heads IMPACT Initiatives, which is part of the ACTED group, read out the names of the victims.

"We ask for the international community to come together to end impunity and to treat every attack against humanitarians as an attack -- and a crime -- against humanity," he said.

World Humanitarian Day is held on the anniversary of the August 19, 2003 attack on the UN compound in Baghdad which killed 22 people.

Since then, nearly 5,000 humanitarians have been killed, wounded or abducted in attacks around the world.