At least 50 armored vehicles carrying Ethiopian troops crossed over into Somalia's Gedo region on Wednesday night, local administration and residents told Radio Dalsan.
The troops are believed to be advancing towards the South West State which will be one of the front lines of an offensive the Somalia government says will rout out militant group Alshabaab.
The arrival of the troops comes less than two weeks after Somalia President Mohamed Abdullahi Farmaajo visited Addis Ababa to request for military backing ahead of the offensive.
The arrival of Ethiopian troops has been received with mixed reaction with some seeing this as a major boost to the planned offensive while others remain critical over the role of Addis in Somalia affairs or their capability to deal with Alshabaab.
Former Defence Minister in the Sheikh Sharif Sheikh Ahmed administration Ahmed Fiqi told Radio Dalsan that he is less optimistic about Ethiopia's ability to restore peace in Somalia.
Farmaajo also sent a similar request to Djibouti and Uganda following Somalia's deadliest single attack that killed more than 400 people on October 14 in the capital Mogadishu.