The UK did not "vote to turn inwards" when it backed Brexit, Prime Minister Theresa May has told the United Nations.

At the UN General Assembly in New York, she said the UK would not "walk away from our partners in the world".

She announced that hundreds of British troops will be sent to Somalia to help combat al-Shabaab jihadists.

And she urged leaders to work together to tackle "the big security and human rights challenges of our time".

Mrs May warned that people felt left behind by the "increasing pace of globalisation".

In her first address to the general assembly, Mrs May said: "We must never forget that we stand here, at this United Nations, as servants of the men and women that we represent back at home.

"And as we do so we must recognise that for too many of those men and women the increasing pace of globalisation has left them feeling left behind.

"The challenge for those of us in this room is to ensure that our governments and our global institutions, such as this United Nations, remain responsive to the people that we serve. That we are capable of adapting our institutions to the demands of the 21st Century."

Announcing the deployment of British troops to Somalia, Mrs May said that Britain had played a "leading role" in the fight against al-Shabaab.

Some 30 training teams will be sent to Somalia, involving up to 70 troops at a time, and a new UK headquarters is to be set up in the Somali capital, Mogadishu.

Previously, just 12 training missions had been planned, with two deployed at present.

The plan involves £7m of funding to improve the skills of the Somali and African Union mission in Somalia (Amisom) forces.

The UK will also use £20m of aid money to help return refugees to Somalia, spending more than half in Kenya which has been housing displaced Somalis.

She said: "Since 2010, with huge support from across the region, and critically the commitment of Somalis themselves, al-Shabaab has been driven from all the major cities it used to control.

"It is vital that as an international community we continue to support countries in the region that are contributing thousands of troops, and that we continue to build the capacity of Somali security forces."

'Job half done'

Mrs May - who also addressed the UN summit on refugees on Monday - said the organisation was "uniquely placed" to tackle war, terrorism, climate change, human trafficking and mass migration.

"The biggest threats to our prosperity and security do not recognise or respect international borders," she said, adding: "And that if we only focus on what we do at home, the job is barely half done."

Mrs May will also hold a series of face-to-face meetings with other leaders and take part in a summit on refugees called by US president Barack Obama.

In his final address to the general assembly, President Obama said countries should do more to help refugees, "even when the politics are hard".

"We have to imagine what it would be like for our family, for our children, if the unspeakable happened to us," he said.

"And we should all understand that ultimately our world will be more secure if we are prepared to help those in need and the nations who are carrying the largest burden with respect to accommodating these refugees."