Dissident Eritrean soldiers with tanks took over the information ministry on Monday and forced state media to call for political prisoners to be freed, a senior intelligence official said.
The renegade soldiers have not gone as far as to demand the overthrow of the government of one of Africa's most secretive states, long at odds with the United States and accused of human rights abuses.
Eritrea has been led by Isaias Afewerki, 66, for some two decades since it broke from bigger neighbor Ethiopia. The fledging gold producer on the Red Sea coast has become increasingly isolated, resisting foreign pressure to open up.
Soldiers forced the director general of state television "to say the Eritrean government should release all political prisoners," the Eritrean intelligence source told Reuters on condition of anonymity.
There was no immediate statement from the Asmara government.
Between 5,000 and 10,000 political prisoners are being held in the country of about 6 million people, the United Nations human rights chief said last year, accusing Eritrea of torture and summary executions.
State media went off air after the call for prisoners to be freed. The government-controlled television station started broadcasting again at around 1845 GMT with a short news bulletin that appeared not to mention the incident.
The mutineers were low- to mid-ranking soldiers who sought a change in the constitution rather than a coup, said one regional expert with close connections in Asmara.
About 200 soldiers with two tanks were involved and they had also surrounded the ministry, diplomats in the region said. It was unclear whether loyalist troops were moving against them.
On a strategic strip of mountainous land, Eritrea is a tightly controlled one-party state. It has more soldiers per person than any country except North Korea.
Eritrean opposition activists exiled in neighboring Ethiopia said there was growing dissent within the army, Africa's second biggest, especially over economic hardship.
"Economic issues have worsened and have worsened relations between the government and soldiers in the past few weeks and months," one activist told Reuters.
A senior European diplomat said there were clear differences between elements of the military and Isaias' administration.
"It is a question of time before the full price of isolation is paid by the government in Asmara. Incidents such as this are mounting," the diplomat said, referring also to economic hardship for most Eritreans.
Despite expectations for a gold mining boom that helped fuel economic growth of nearly 8 percent last year, per capita gross domestic product is less than $550 a year.
Shares in gold companies with mines or projects in the country fell sharply on Monday. Toronto-listed Nevsun Resources Ltd was down 9 percent. Those in smaller explorer Sunridge Gold Corp were down over 26 percent.
Chalice Gold also has a presence.
Eritrea split from Ethiopia in 1991 and relations between them are perennially strained.
Asmara has also accused the United States, a staunch ally of Ethiopia, of trying to topple Isaias. A U.S. diplomatic cable released by Wikileaks described him in 2009 as an "unhinged dictator". He survived an assassination attempt by a disgruntled soldier the same year, diplomatic sources said.
Isaias has also accused the United States of spreading lies that he is sick. He has no obvious successor.
"Isaias, sick or not, is a wily survivor and it would be a mistake to prematurely write him off," said J. Peter Pham, director of the Michael S. Ansari Africa Centre at the Atlantic Council.
"On the other hand, there are few prospects of any amelioration of the economic crisis which, as it worsens, cannot but affect the relationship between the dictatorship and the forces that keep it in power."
The United Nations' Security Council imposed an embargo on Eritrea in 2009 over concerns its government was funding and arming al Shabaab rebels in neighboring Somalia - charges Asmara denied.