Scattered skirmishes broke out when hundreds of people gathered in downtown Yerevan to mark the end of emergency rule.
RFE/RL's Armenian Service reported that a heavy police presence greeted people who turned out to honor eight people killed when security forces dispersed opposition-led protests three weeks ago.
RFE/RL's Yerevan bureau said opposition figure Arakel Semerjian -- a relative of opposition leader Levon Ter-Petrossian, who claims his presidential bid was thwarted by official fraud in the February 19 election -- was detained by police in one of the confrontations.
Ter-Petrossian remains under de facto house arrest, his movements restricted by security forces around his home.
A senior U.S. official, speaking ahead of the lifting of the state of emergency, highlighted international concern over the risk of a collapse in that country's political dialogue, warning that Armenia still has work to do to "get back on the democratic path."
Outgoing President Robert Kocharian declared emergency rule on March 1, when fatal clashes left at least seven civilians and one policeman dead in the worst civil violence in Armenia's post-Soviet history.
Kocharian announced at a news conference hours before the clampdown was lifted overnight that there was "no reason to extend the state of emergency" and that "normal life" would return to the capital on March 21.
A new law that was passed this week, however, gives authorities the right to ban demonstrations if they pose a threat to public order.
Kocharian defended his decision to declare emergency rule and looked ahead to the upcoming transfer of power to President-elect Serzh Sarkisian.
"My task now is the stabilization of the entire situation. It should be brought back, in terms of manageability, to the condition that we had before the elections," Kocharian said. "The question here, of course, is not about the psychological factor, which will require more time. [There is a] need to transfer power to the newly elected president under manageable conditions. And this is how it will be."
Security forces on March 21 guard a downtown site where demonstrators and police clashed three weeks earlier
Official results showed Sarkisian, the current prime minister, defeating opposition candidate Levon Ter-Petrossian by a wide margin in the February 19 poll that critics say was marked by widespread falsification.
The opposition has claimed the civilian death toll when security forces dispersed protesters on March 1 was much higher and that police initiated the violence.
Watchdog groups such as Human Rights Watch and Freedom House have condemned the violence and called on authorities to investigate the use of force.
Some international observers have warned that the fissure between the Armenian government and the opposition appears deeper and the danger of further violence much higher than in neighboring Georgia -- where street protests and a state of emergency preceded President Mikheil Saakashvili's reelection in the face of fractured opposition in January.
In an interview with RFE/RL on March 20, U.S. Assistant Secretary of State for European and Eurasian Affairs Daniel Fried urged Armenia to "pull itself together and get back on a democratic path."
"We welcome the lifting of the state of emergency, but there are other problems and these need to be addressed," Fried said. "People who have been arrested for rioting and violent actions, that's one thing. But people who have been arrested for more questionable reasons need to be let go -- there needs to be normalization; there needs to be a dialogue with the opposition. Look, this is a troubling situation for all of Armenia's friends."
Armenian prosecutors announced on March 19 that they had arrested 106 people for allegedly plotting to stage a coup during the postelection protests. Some 800 more have been brought in for questioning.
Opposition leaders dismiss the coup allegations and say that many of those arrested were supporters of Ter-Petrossian whose arrests were politically motivated. Detainees include members of parliament and a former foreign minister.
The state of emergency banned public gatherings and imposed press restrictions.
RFE/RL's Armenian Service contributed to this report