In recent weeks, Somali insurgents have stepped up attacks on the Ethiopian army and the Somali transitional government it is backing.
For BBC World Service's Assignment programme, Rob Walker went in search of the Islamist movement playing an increasingly deadly role in the conflict.
In the past few weeks insurgents have taken over a series of towns, killing government soldiers, stealing weapons, and then withdrawing.
But it has become clear there are deep divisions within the insurgency over which direction it should take, with many of the recent attacks attributed to one group - a radical Islamist organisation called al-Shabab, meaning "The Youth."
Since the insurgency began, al-Shabab has rarely met Western journalists - but after protracted negotiations, one member agreed to meet me.
He is the commander of a cell of al-Shabab fighters. I am not allowed to give his name, or say where it is.
"There are al-Shabab fighters in all parts of the country," he says.
"I don't want to talk of numbers. But when the Ethiopian troops first arrived we were already strong.
"Now we have even more power because now we have the support of the people everywhere."
Like many insurgents, he headed to Mogadishu to fight the Ethiopians as soon as they entered the capital in December 2006, ousting the Union of Islamic Courts which had taken control of much of southern Somalia.
"We attacked them that same night," he recalls.
"With God's grace we defeated them in that first battle. At that time I was happy because I was hoping to become a martyr."
He adds he has two aims - to become a martyr and to ensure that the country is governed by Sharia law.
"As al-Shabab, we don't care about people who don't want Sharia law," he says.
"Our goal is to have Sharia as the permanent law of our country, and to get the infidels out of our country, whether they are Ethiopians or Americans."
His message to those Somalis who do not pray five times a day is clear.
"First of all, we will call them to return to Islam and pray - because what differentiates a Muslim and a non-Muslim is praying five times," he says.
"If they refuse we will call them again and again to pray. If they entirely refuse, we will jail them and we will keep them without food until they return to praying."
He denies that al-Shabab has any links with al-Qaeda, although he says that "they are Muslims so they are our brothers".
"Our common objective is to have Sharia law as the law of our country. Al-Qaeda wants that and we want that," he adds.
But many Somalis do not share al-Shabab's vision for an Islamic state in Somalia.
The Islam practiced in Somalia has traditionally been moderate and tolerant. Local cinemas, for example, thrive, showing Bollywood films featuring scantily-clad women.
There is no history of widespread support for radical religious movements, and this is why al-Shabab's ideology is at odds with that held by many Somalis.
But al-Shabab does not tolerate dissent.
One 25-year-old woman, who did not want her name revealed, says that in late 2006 - when the Union of Islamic Courts were still in control of Mogadishu - al-Shabab ordered a cinema near her house to close.
A young boy who was a relative staying with her family spoke out against the decision. As a result, al-Shabab soon came to look for him.
"There were many of them - they came to our house in two pick-up trucks," she recalled.
"Then two of the men came and knocked on the door. I opened it - and they said, 'bring the boy out of the house.'
"I said: 'The boy is not here'. They said: 'Bring him out.' I told them: 'He's not here.' Then they started kicking me, they kicked me to the ground.
"Then they started shooting."
"They shot me three times in the legs - one into my right leg then two into my left. It was terrible, my mother was in the house and she shouted: 'Why are you shooting my girl?'. They started beating her. They threw my mother on the ground and they kicked her."
Her legs are still badly wounded; they have been infected for a year and a half.
The cinema was closed, and those who had been using it had their heads shaved to mark them out.
And I have been speaking to people in Somalia and outside who have had relatives killed by al-Shabab.
Some were killed because they were accused of collaborating with the transitional government, or Ethiopians, sometimes in the most minor ways - one man said his brother was killed for selling phone cards to Ethiopian troops.
None of the relatives I spoke to were prepared to do an interview, all saying they feared reprisals against them or their family.
In 10 years of visiting Somalia, what is really striking is not just the growth in extremism in the country but the fear among ordinary Somalis to talk about it.
One of the most senior al-Shabab commanders is Muktar Ali Robow.
He keeps his location within Somalia secret, and constantly changes his phone number for security reasons.
When I tracked him down, he claimed that the "media is exaggerating" the killings of Somali civilians by al-Shabab.
"All we do is we kill the Ethiopians, we don't kill civilians," he said.
"We are killing the enemy of Allah, and until we get them out of the country we will continue doing so... those people who are telling you their people have been killed they are wrong.
"They are working for the Ethiopians, we never kill ordinary people."
He added that he believes people are not talking publically, not because they are afraid, but because they support al-Shabab.
"You can see that, because when the Ethiopian-backed forces of the government go somewhere, the people flee - that's because those troops rob and kill," he said.
"But wherever we go, people say "Allah Akbar." They are happy to see us."
The reality is that civilians are now trapped - between the forces of Ethiopia and the transitional government on one side and insurgents on the other.