Somalia's government and the country's Islamist movement are blaming each other for the collapse of peace talks in Sudan on Wednesday.
The accusations were made Thursday as both sides prepared for further conflict that diplomats fear could turn into a full-scale war.
Somali government officials say Islamist leaders sabotaged the talks so their militias could attack the government's home base of Baidoa and seize control over all of Somalia.
The Islamists say the talks collapsed because Ethiopia refuses to withdraw forces it sent to Somalia to protect the government.
Reports from southern Somalia say the Islamists have sent more fighters to their lines outside Baidoa. The French news agency, AFP, quotes an Islamist commander, Mursal Haji Ali, who says his forces are ready for a full-scale attack.
Mediators at the failed peace talks in Khartoum have called for restraint on both sides.
Militia groups loyal to Somalia's Islamic courts have seized control over much of the country's south since winning a battle for the capital, Mogadishu, in June. Somalia's interim government has international support but virtually no power outside Baidoa.
Diplomats fear that open warfare between the two sides could draw in Ethiopia and Eritrea, and could trigger war across the Horn of Africa. Ethiopia has vowed to support the Somali government, while the United States has accused Eritrea of arming the Islamists. Eritrea has rejected that charge.
Some information for this report was provided by AFP and Reuters.