Britain will take in four thousand refugees from camps on the Syrian border, according to the UN refugee agency.
Prime Minister David Cameron earlier revealed Britain would take in "thousands more" refugees in the face of growing public and political pressure to respond to the migration crisis unfolding across Europe.
Mr Cameron did not give a specific figure, but said he would set out more detailed plans next week, and that Britain would act with "our head and our heart".
Speaking during a visit to Portugal, Cameron said: "We have already accepted around 5,000 Syrians and we have introduced a specific resettlement scheme, alongside those we already have, to help those Syrian refugees particularly at risk.
"As I said earlier this week, we will accept thousands more under these existing schemes and we keep them under review.
"And given the scale of the crisis and the suffering of the people, today I can announce that we will do more - providing resettlement for thousands more Syrian refugees."
Reacting to Mr Cameron's remarks, UN refugee agency spokeswoman Melissa Fleming said: "We welcome very much the move to increase resettlement spaces for Syrians in the UK.
"Those spaces are going to be critical to the lives and future of 4,000 people."
Britain has faced criticism for refusing to join an EU scheme to resettle migrants and has failed to match Germany and Sweden, which have opened their doors to large numbers of refugees.
Previously, Mr Cameron said his Government was opposed to letting more refugees come to Britain.
But speaking on Friday the PM defended Britain's response, saying the country has helped refugees throughout its history.
"We are already providing sanctuary and we will continue to do so," he added.
Mr Cameron also said Britain had provided around €1.2bn in aid to war-torn Syria, more than any other European nation.
However, the PM gave no indication Britain would be willing to resettle any migrants from other countries who have made perilous journeys across the Mediterranean to get to Europe in recent months.
SNP leader Nicola Sturgeon earlier urged Mr Cameron to deliver an "immediate humanitarian response", while a senior UN official said Britain and other EU countries must develop a common plan for relocating refugees.
In a letter to Mr Cameron, Scotland's First Minister warned that the death of three-year-old Kurdish-Syrian refugee Aylan Kurdi highlighted his moral obligation to offer sanctuary to those fleeing conflict and persecution.
An emergency refugee summit organised by Ms Sturgeon and scheduled to take place on Friday was set to bring together charities and religious groups to set out what Scotland can do to help.
Antonio Guterres, UN high commissioner for refugees, said the EU is facing a defining moment and must "mobilise full force" towards a common approach.
In clear criticism of Britain's stance on the crisis, French president Francois Hollande warned some countries were not "shouldering their moral obligations".
European Council president Donald Tusk, seen as an ally of the PM, added further pressure by stating that "all EU members" needed to take their share of refugees.
Mr Cameron was also criticised by contenders for the Labour leadership during a televised Sky News debate.
Liz Kendall accused the Prime Minister of being "heartless and powerless" in his handling of the migration crisis, while Jeremy Corbyn said that the UK providing refuge to 4,000 people was "not enough".
Shadow home secretary Yvette Cooper, who has suggested the UK could take 10,000 more refugees every month, said: "Other countries are doing their best. We have got to do more as well."
The British Red Cross has launched an emergency appeal in the face of "one of the biggest humanitarian disasters of our time".
Head of emergencies Ben Webster said: "We urgently need supplies such as food, water, nappies and hygiene kits as well as emergency medical treatment - your support can make a huge difference."
On Friday, Ireland announced it would treble its refugee intake to at least 1,800 over the next two years.
