The United Nations High Commissioner for Refugees (UNHCR) warned on Friday that the number of Syrians who have fled their own land to seek refuge in other states is growing very fast in the face of intensifying conflict in Syria.

"UNHCR was able to witness the dire humanitarian situation of these displaced families," agency spokesman Dan McNorton said in Geneva.

"Due to the poor sanitation and hygiene conditions in which people were living, many, especially children, were suffering from diarrhea, respiratory problems, high fevers, ear infections and skin diseases," he said.

The spokesman said that more than 100,000 refugees crossed the Syrian border just in the last 15 days.

On May 19, the UN warned that the number of Syrian refugees could double and reach three million people by the end of this year if the unrest does not end.

UN figures also show that more than four million Syrians have been internally displaced since the beginning of the unrest in the Arab country more than two years ago.

UNHCR says it has registered close to 1 million refugees since the start of 2013 alone, which amounts to about 250,000 people each month.