Burundi has again delayed the planned deployment of 2,000 troops to Somalia, as part of an African Union (AU) peacekeeping force.
Only Uganda has sent troops to Somalia so far
The soldiers are ready to go but communications and transport equipment promised by the US and France had not arrived, an army spokesman said.
Just 1,600 Ugandans are in Somalia of the planned 8,000-strong AU force.
They have unable to stop daily attacks by Islamists and other insurgents, especially in the capital, Mogadishu.
In the latest incident, two civilians were killed and three others, including two government soldiers, were wounded by a suspected remotely controlled land mine explosion, which targeted a government army vehicle near the airport.
"A young girl was killed by shrapnel as she was standing at the window of their house and a woman was also killed in the explosion, I saw both of them," said local resident Mohamed Dilahow.
The deaths come as UN Somalia envoy Francois Fall visited Mogadishu to support the ongoing reconciliation conference.
"I request once again, the chairman of the conference to convince and open the doors of the conference to all the stakeholders in Mogadishu and outside the country, those who are ready to reject the violence," he told some 1,000 delegates.
He also promised that "the UN and the international community will contribute whatever technical assistance is needed to ensure that you reach decisions for peace".
Violence has flared in Mogadishu over the past month
Earlier, Mr Fall held closed-door talks with President Abdullahi Yusuf and Prime Minister Ali Mohamed Ghedi.
Islamists and members of Mogadishu's dominant Hawiye clan say they will not attend the conference until Ethiopian troops leave the country.
Ethiopia says it will withdraw when the AU force is big enough.
The Burundian troops had been due in July. Nigeria and Ghana have also promised to contribute to the AU force.
The Ethiopians helped the government oust the Union of Islamic Courts (UIC) last December.
The UIC had controlled Mogadishu and much of southern Somalia for six months.
Eritrea has denied claims it is arming the Islamists.
Some 10,000 residents have fled Mogadishu in the past month following an increase of violence in the city since reconciliation talks began, according to the UN.
A report by the UN says there are many more arms in Somalia than at any time since the civil war began in 1991.