"Since 18 February, we estimate that between 10,000 and 11,000 families [60,000-66,000 people] have arrived in Mogadishu, fleeing fighting or the fear of fighting in their home areas," said Abdullahi Shirwa, head of the government's National Disaster Management Agency.
Most new arrivals are coming from the Afgoye corridor, "but a significant number are coming from the towns of Beletweyne and Baidoa [which were recently liberated from Al-Shabab by Ethiopian forces supporting the Transitional Federal Government]".
Shirwa said there was a likelihood that more displaced would be coming to Mogadishu in the next few weeks if the conflict in Bay, Bakool, Middle and Lower Juba (southern Somalia) escalated.
As famine conditions have ended in the country, many of the displaced have begun to return home but the renewed fighting in parts of southern Somali will make it impossible for many, said Shirwa. "We should not be talking about resettlement in the midst of conflict but rather emergency assistance to those who are coming daily."
A local journalist in the town of Baidoa, who requested anonymity, told IRIN many residents were leaving. "People are afraid and don't know what to expect so they are leaving. I think it is driven more by uncertainty of what to expect from their new rulers and the fact that any young man is suspected of being Al-Shabab until they prove otherwise," he said.
A civil society activist told IRIN that as the military pressure on areas under Al-Shabab control increased, the likelihood of more displaced coming to Mogadishu would also increase.
"I have seen people who left Merka [100km south of Mogadishu] and they told us that they were running from the military activities in the area. They don't want to get caught in the middle."
She said unknown airplanes and helicopters were flying over many parts of the southern Somalia "and it is scaring people", adding that they were also leaving "because they cannot access much humanitarian assistance in Al-Shabab territory. We were planning for massive returns but that now is not going to be possible."
Hawo Abikar, a mother of five, came to Mogadishu 10 days ago from the Lower Shabelle region with nine other families. "We left our home near Janaale town because we were afraid. There are so many planes flying low and Al-Shabab is forcing people to join the fighting."
She said they had to sneak out of town at night because Al-Shabab "does not allow anyone to leave but I am sure many more will leave because everyone is afraid of what is coming".
Al-Shabab still controls much of southern Somalia, despite pressure from the Ethiopian, Kenya, African Union and TFG forces.
So far, the displaced are staying in a temporary camp in the south of the city, said Abikar.
"Fearing the worst"
An elder, who requested anonymity, said he had left Afmadow "because these people [Al-Shabab] have no respect for tradition or elders. People don't know what to expect from them, so they fear the worst."
Conflict and drought have led to the worst humanitarian crisis the country has faced in nearly two decades. An estimated 3.6 million - almost half the total population - need aid, according to the UN.
The UN Refugee Agency (UNHCR) estimates the number of IDPs in Somalia at approximately 1.36 million.
"Humanitarians are concerned about the impact of large-scale population movements from the Afgoye corridor on the fragile humanitarian situation in Mogadishu, where displaced people are already living in precarious conditions," said Russell Geekie, head of public information at the UN
Office for the Coordination of Humanitarian Affairs, Somalia.
"An escalation of hostilities deeper into the Afgoye corridor will likely lead to an additional influx of tens of thousands of people into Mogadishu, straining the capacity of the camps and host communities," he told IRIN by email.
"Humanitarians in Mogadishu are doing everything within their capability to provide immediate help to those most in need, wherever they are. They have also been assessing the capacity of existing assistance structures and stocks available to extend assistance to the additional population in need and target, in particular, the most vulnerable families."