Doctors in the Somali capital, Mogadishu, say they are struggling to cope after gun battles left at least 60 people dead and scores injured.
Both sides are using the lull to rearm
One doctor told the BBC he was unable to reach the building where the drugs are stored in the city centre.
A BBC correspondent in the city says there is only sporadic gunfire but there are fears the fighting could resume at any time.
Islamist militias captured some territory from an alliance of warlords.
The BBC's Mohammed Olad Hassan in Mogadishu says thousands of people are fleeing their homes - some for less dangerous parts of the city, others away from Mogadishu.
Our correspondent says both sides are using the lull in the fighting to rearm and strengthen their positions.
Somalia has had no fully functioning government since the overthrow of President Siad Barre in 1991.
This year's clashes have been the worst in the capital for more than a decade, leaving some 200 people dead.
Our correspondent says the south of the city is quiet, after the Islamists seized the key K4 junction and a nearby hotel from the warlords of the Anti-Terrorism Alliance.
The loss of the junction on the main north-south roads means the warlords have great difficulty moving their fighters around the city.
There is some gunfire in northern districts, where the bulk of this month's fighting has occurred.
"There were large movements of militiamen overnight," K4 resident Mumi Ibrahim told the AFP news agency.
"They are preparing for another round. If they don't start fighting today, they will start tomorrow, but definitely there is no peace at the moment."
Dr Abdi Ibrahim Jiya of the Somali Doctors' Association said that 60 people had been killed in Thursday's fighting and 150 wounded.
Witnesses said mortars and heavy machine-guns were being fired indiscriminately, with most casualties being civilians caught in the crossfire.
On Thursday, K4 resident Abdifatah Abdikadir told Reuters news agency that people were being carried on wheelbarrows to the hospital with broken limbs and gunshot wounds.
Anti-Terrorism Alliance member Ibrahim Maalim told Reuters: "The fighting is very heavy... I have never seen such a heavy exchange. Mogadishu is blazing with fire."
Our correspondent says the fighting has been fuelled by a widespread belief that the warlords are being backed by the US.
The US merely says it will support those trying to stop "terrorists" setting up but stresses its commitment to the country's transitional government, which functions from Baidoa, 250km (155 miles) north-west of the capital.
More than 140 people died in eight days of fighting earlier this month, mostly around the CC district of north Mogadishu.
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