The United Nations' refugee agency reports a dramatic rise in the number of refugees fleeing to Kenya from Somalia, due to the recent insecurity there.

Until this week, there were an average of 100 Somalis coming into Kenya each day. The U.N. refugee agency transported them to Dadaab, a complex of three camps already hosting 134,000 refugees, mainly Somalis.

But a spokesman for the Nairobi office of the U.N. High Commissioner for Refugees, Emmanuel Nyabera, tells VOA that since Wednesday, more than 2,000 Somali refugees have arrived at the Kenyan border crossings of Liboi and Amuma.

"We are getting extremely concerned about the numbers of refugees who are coming into Kenya from Somalia at the moment. The problem is that, if these numbers continue to grow, then even the camp itself will not be able to accommodate these new arrivals. And, that would mean that we have to consult with the government of Kenya to see, if we can have an extra camp, but within Dadaab camp," he said.

According to UNHCR figures, more than 30-thousand Somali refugees have fled to Kenya this year.

The agency says this week's sharp increase in the number of refugees is likely due to reports of an advance by militias loyal to the Union of Islamic Courts into the Juba Valley towns of Afmadow and Buale.

About 20 percent of those coming in through the Amuma border crossing are urban merchants from Kismayo, who say they have lost their businesses, the agency reports.

The agency says the rest are herder families from Lower Juba, and about 40 percent of those arriving at the Liboi crossing are Somali Bantus.

The Union of Islamic Courts rose to prominence earlier this year, and have been capturing key areas of Somalia, including the capital, Mogadishu, posing a serious challenge to Somalia's transitional government.

The transitional government has international backing, but virtually no power outside its base of Baidoa.

Last week, the Islamic courts captured the port city of Kismayo, about 150 kilometers east of the Kenyan border. The Kenyan government has recently stepped up its border and sea patrols.