As tension soared anew fuelling fears of large-scale conflict, the Islamists shut down border crossings in Somalia's central Hiran region for "national security reasons" and put down a new protest against their rule in the south.
"The border with Ethiopia is closed in the Hiran region for national security reasons," deputy regional security chief Sheikh Hussein Mohamud Gagale said.
"Ethiopian soldiers are conducting military manoeuvres around Sarirale village, which is inside Somali territory," he told Mogadishu's Simba radio, noting that Sarirale is about 45 kilometres from the border.
"They also planted landmines around the border areas," Sheikh Gagale said.
"The mines could kill our people and animals so we have taken the decision to block the border."
There was no immediate reaction from Ethiopia but on Thursday, after the Islamists accused Ethiopian forces of shelling the nearby border town of Beledweyne, Addis Ababa repeated denials of any military presence in Somalia.
Beledweyne is about 30 kilometres from the Ethiopian border and 300 kilometres north of Mogadishu, which the Islamists seized from warlords in June and have used as base for rapid expansion.
Mainly Christian Ethiopia is wary of the rise of the Islamists who it accuses of being "jihadists" and is backing Somalia's weak transitional government and its calls for the deployment of a regional peacekeeping force.
The Islamists are vehemently opposed to peacekeepers and have vowed to fight any foreign troops on Somali soil, particularly those from Ethiopia, as they move to cement their hold on southern and central Somalia.
In the key southern port of Kismayo, residents and officials said Islamist gunmen had opened fire and arrested more than 20 people in the early hours of Saturday morning as they put down a new protest against their seizure of the town last month.
Heavily armed gunmen fired into the air to disperse several hundred chanting demonstrators who burned tires and threw stones to show their opposition to the taking of the port by the Islamists on September 24, they said.
"I was among the protesters when the Islamic gunmen shot at us," Farhan Ahmed said, one of the demonstration's organisers.
"Fortunately, no one was hurt but everybody was shocked."
He said as many as 40 people had been detained by the Islamists who have rapidly expanded their territory to include most of southern Somalia since seizing Mogadishu in June.
But Ahmed Abdulkadir, an elder who was trying to secure the release of the prisoners, put the number of detainees at 21.