Liberia's court has charged a former army chief and a former speaker of the parliament with treason, officials say.
Ellen Johnson-Sirleaf took power last year after winning elections
They say General Charles Julu and ex-House Speaker George Koukou will remain in custody pending a trial.
They were arrested in connection with an alleged coup against the government of President Ellen Johnson-Sirleaf, who took power in 2006 after years of war.
Under Liberian law, the two men could face the death penalty or life in prison, if convicted.
The BBC's Jonathan Paye-Layleh in the capital, Monrovia, says people are shocked at the possibility of renewed unrest in the country.
The United Nations has some 15,000 peacekeepers in Liberia - the second largest deployment in the world.
Gen Julu headed the presidential guard under former leader Samuel Doe and led a 1994 coup attempt.
Mr Koukou was the speaker of Liberia's National Assembly during a post-war transitional government.
They were two of five people arrested in connection with the alleged coup, Deputy Information Minister Gabriel Williams said.
Officials said that former Col Andrew Dorbor, one of the detained men, said during questioning that Gen Julu had asked him and one other person to travel to Ivory Coast to smuggle weapons into the country.
On Friday, investigators released a video tape that was secretly recorded by Liberian intelligence services last month.
It apparently showed Mr Dorbor and another person holding discussions with an Ivorian border commander on how to transport weapons in Liberia.
It was not immediately known when the trial would start.