Ethiopian troops ousted Islamist forces from Mogadishu in 2006
Ethiopia's government has admitted it has "reconnaissance missions" in Somalia, but denies it is re-deploying its troops in the country.
Several thousand Ethiopian troops left Somalia in January after a controversial, two-year intervention in support of the UN-backed government.
But two weeks ago, several witnesses near the border said they had seen Ethiopian troops digging in.
Those reports came after Islamist insurgents made several advances.
"We have no plans to go back to Somalia... [but] there are reconnaissance missions," Information Minister Bereket Simon told reporters.
"When there is a threat, you can send some scouts here and there," he added.
'Right to intervene'
This is the first time Ethiopia has admitted that its troops have crossed back into Somalia since they withdrew under a UN-brokered peace deal five months ago.
When its troops left, Ethiopia made it clear it did still reserve the right to intervene if its interests were directly threatened.
Mr Bereket noted with approval a recent brief counter-offensive by pro-government forces in Mogadishu against the radical Islamist insurgents of al-Shabab, which is accused of links to al-Qaeda.
"[This] indicates all is not rosy for al-Shabab," said the Ethiopian government spokesman. "The terrorists have lost momentum for the time being."
There have been several reports of the Ethiopian military crossing into Somali territory for hot-pursuit operations, or to check vehicles moving in the border area.
Since withdrawing at the beginning of the year, Ethiopian troops have kept up a strong presence along the Somali border.
Ethiopia, a US ally, invaded its war-torn neighbour in December 2006 to prop up the transitional government and initially everything went according to plan.
Rebel resistance melted away before the 3,000-strong Ethiopian advance and the Somali government was able to set up in Mogadishu.
But the administration did not extend its control and the Islamists continued to launch deadly attacks on both Ethiopian and Somali government forces.
About 4,300 Ugandan and Burundian peacekeepers from the African Union are in Mogadishu, having taken up positions vacated by the Ethiopians in January, but without any mandate to pursue the insurgents.
Analysts say they are only in effective control of the presidential palace, airport and seaport in Mogadishu, while the Islamist guerrillas control chunks of the capital, along with swathes of central and southern Somalia.