Two weeks after al-Shabab said a ban on certain aid groups working in Somalia would be lifted, the Islamist group has announced that the ban remains in place, the AFP news agency has reported.
The group also rejected a United Nations declaration that parts of the country had been hit by the worst famine seen in the area for 20 years.
Al-Shabab, which controls parts of the affected region, accused the UN of exaggerating the severity of the drought and using it as propaganda.
"Those earlier banned groups are not welcome to serve in our area of control," Shabab spokesman Sheikh Ali Mohamud Rage said in a broadcast on the Islamist Al Furqaan radio on Friday. "There is drought in Somalia but not famine - what is declared by the UN is 100 per cent false."
"The declaration of famine is political and is a lie with hidden agendas," he added, saying only that there has been "a shortage of rain".
The UN's World Food Programme (WFP), one of the aid groups banned by al- Shabab, said on Friday that it would fly aid into the capital "within days".
Somalia is the worst affected country in the drought-hit Horn of Africa region, where the UN says that more than 3.7 million people are at risk of starvation.
Al Jazeera's Peter Greste, speaking from a refugee camp in Dolo Ado, Ethiopia, said he could neither confirm or deny al-Shabab's claims about the extent of the drought but that the refugees at the camps he had been to needed quicker services and more aid.
"It's very difficult to confirm exactly what is going on in Somalia," he said.
"[Refugees] are still arriving at a rate of about 1,500 a day [at Dadaab refugee camp, the largest in the world, in Kenya].
"There are 11,000 refugees [in Dolo Ado] alone who still have to be processed."
Two weeks before Friday's announcement, Al Shabab said aid would be allowed in by all aid organisations.
Rozanne Chorlton, UNICEF's co-ordinator in Somalia, told Al Jazeera on Wednesday that UNICEF has been allowed to deliver aid unhindered in al-Shabab-controlled areas over the past fortnight, but that "it may be more difficult for organisations that were not already in areas affected".
Al-Shabab, which is aiming to overthrow the government and impose Sharia law, imposed a ban on the WFP in February 2010, saying that they had received complaints from local farmers that the WFP's food aid made it harder for them to sell their own products at a sustainable price.
The rebel group said in 2010 that some food distributed by the WFP had already past its expiry date and caused illnesses among aid recipients.