Heavily armed Ethiopian troops with several army trucks have reportedly crossed the border into central Somali regions of Hiran and Galgadud, residents and reports said.
Residents of Balanbale town in central Galgadud region said they have seen Ethiopian military forces backed by army vehicles in the outskirts of the town.
One resident said the troops have dug trenches in positions without prior notice of the elders.
Ethiopian troops have also crossed the border and reached Kalabeyr town in Hiran region, about 22km (14 miles) from the Somali-Ethiopian border, according to locals.
A resident told Garowe Online "a lot of troops arrived in the area on early Saturday and have started making military manoeuvring."
Ethiopian troops have in the past carried out military incursion into central Somalia to oust Islamist militant groups fighting the embattled UN-backed Somali government.
Since withdrawing from Somalia early this year, Addis Ababa amassed its troops along the border and kept watchful eye on political development in the war-torn country.