The head of the UN refugee agency warned on Monday that displacement crises in Lebanon and Sudan could worsen, but said tighter border measures were not the solution, calling them ineffective and sometimes unlawful.

Addressing more than 100 diplomats and ministers in Geneva at UNHCR's annual meeting, Filippo Grandi said an unprecedented 123-million people are now displaced around the world by conflicts, persecution, poverty and climate change.

"You might then ask: what can be done? For a start, do not focus only on your borders," he said, urging leaders instead to look at the reasons people are fleeing their homes.

"We must seek to address the root causes of displacement, and work toward solutions," he said. "I beg you all that we continue to work — together and with humility — to seize every opportunity to find solutions for refugees".

Without naming countries, Grandi said initiatives to outsource, externalise or even suspend asylum schemes were in breach of international law, and he offered countries help in finding fair, fast and lawful asylum schemes.

Western governments are under growing domestic pressure to get tougher on asylum seekers and Grandi has previously criticised a plan by the former British government to transfer them to Rwanda.

In the same speech he warned that in Lebanon, where more than one-million people have fled their homes due to a growing conflict between Israel and Hezbollah, the situation could worsen further.

"Surely, if airstrikes continue, many more will be displaced and some will also decide to move on to other countries."

He called for a drastic increase in support for refugees in Sudan's civil war, saying lack of resources was already driving them across the Mediterranean Sea and even across the Channel to Britain.

"In this lethal equation, something has got to give. Otherwise, nobody should be surprised if displacement keeps growing, in numbers but also in geographic spread," he said.

The UNHCR response to the crisis that aims to help a portion of the more than 11-million people displaced inside Sudan or in neighbouring countries is less than 1/3 funded, Grandi said.

The number of displaced people around the world has more than doubled in the past decade.

Grandi, set to serve as high commissioner until December 2025, said the agency's funding for this year had recently improved due to US support but remained "well below the needs".