If confirmed, this appears to be the largest Ethiopian deployment since the 2009 withdrawal which followed an invasion that was very unpopular with ordinary Somalis. If Ethiopian soldiers were to deploy deep inside Somalia, this would increase the pressure on al-Shabab.
Further south, the Kenyan army is working with Somali militias in what appears to be an effort to push al-Shabab away from the border and possibly out of the lucrative port of Kismayo.
One MP from central Somalia said he could not confirm exactly where the Ethiopian troops had reached or in what number. But he said their presence was vital in order to help defeat al-Shabab.
History shows that military intervention in Somalia is hugely unpopular and can act as a catalyst to unite Somali groups that had been enemies.
Although al-Shabab's strict version of Islamic law is unpopular with most people, that does not mean Somalis will welcome Kenyan and Ethiopian soldiers. This could hamper their effort to defeat the militants.
Aid agencies have warned that an escalation in fighting could further jeopardise the efforts to get food to victims of the drought and famine.
On Friday the UN said the humanitarian effort had improved the situation but we are told almost a quarter of a million Somalis still face imminent starvation