Hundreds of Somali refugees who fled heavy fighting in the capital, Mogadishu, are stranded near the Kenyan border in a desperate condition.
Aid agencies have been unable to reach the stranded Somalis
A BBC correspondent says six children died following a diarrhoea outbreak in Doble town where they are camped.
Kenya closed its borders with Somalia last year and insists it will not accept the fleeing families.
Two sets of talks have taken place about the crisis which the UN says has forced up to 100,000 to flee Mogadishu.
The UNHCR says 400 people have died in what the International Committee of the Red Cross has described as the worst fighting for 15 years in Mogadishu.
Battle for treatment
The BBC's Bashkas Jugsodaay in the Kenyan town of Garissa says most of the refugees on the border trekked from Mogadishu and lack food, medicine and a supply of fresh water.
50,000: Lower Shabelle
17,000: Middle Shabelle
17,000: Afgooye, 30km west of Mogadishu
10,000: Marka, 60km south-west of Mogadishu
2,700: Galkayo, 700km north-west of Mogadishu
2,000 (unconfirmed): Doble, on Kenyan border
Source: UNHCR; estimated figures
Aid agencies are unable to reach the stranded families as security personnel manning the Kenyan border with Somalia have denied them access, our reporter says.
The UN says some 47,000 people have fled Mogadishu in the last two weeks alone.
Those displaced people in the Shabelle region without relatives or clan links are living under trees.
Further south in the port city of Kismayo, those fleeing have met a hostile reception and residents are reportedly charging for the use of shade under trees.
A ceasefire between Ethiopian troops and insurgents has held for a second day in Mogadishu as hospitals battle to treat victims of the four-days fighting.
A committee of elders from the Hawiye clan, which controls the capital, held talks with Ethiopian commanders.
Fighters linked to the Hawiye clan and militant Islamists who have been battling with Ethiopian and interim government troops are however, keeping vigil at their strongholds in the capital.
The two sides agreed to maintain the ceasefire to allow the removal of dead bodies and then return for more talks on Thursday, Reuters news agency reports.
Meanwhile, the US-led International Contact Group (ICG) for Somalia has been meeting in the Egyptian capital, Cairo.
The diplomats from Africa, the Arab world, the US and Europe said the tentative ceasefire should be strengthened.
Norway said Ethiopian troops in Mogadishu were exacerbating the situation and should withdraw as soon as possible.
The Arab League's Secretary-General Amr Moussa said the humanitarian crisis prompted by the fighting also needed to be tackled and called for reconciliation.
A national reconciliation conference has been set for later this month.
Last week, Somali Prime Minister Mohammed Ali Ghedi said moderate Islamic scholars who have denounce violence and recognise the transitional charters have been invited to participate at the talks.
The ICG has been pushing for moderate leaders of the ousted Union of Islamic Courts to be included in Somalia's transition process.
Six months of order imposed by the Islamists ended when they were ousted by Ethiopian troops in December.
Some 1,700 Ugandan troops are in Mogadishu as the advance party of an 8,000-strong AU force, which is supposed to replace the Ethiopian troops as they gradually withdraw