Witnesses reported heavy gunfire started about midday local time.
State radio played traditional music, and made no mention of the coup attempt. Soldiers and armored vehicles were seen near the palace and nearby streets were deserted.
Official sources in the capital Niamey tell VOA's Hausa Service that people have been taken to the hospital.
Government ministers were scheduled to gather at the palace for a meeting about that time.
The alleged arms dealer to the world, Viktor Bout, could face another extradition hearing in Thailand after new charges were filed against him in New York. The possibility comes after a Thai court ruled it could not extradite Bout to face charges in the United States of supporting terrorism.
Thailand's attorney general's office on Thursday said it could file another extradition case against suspected Russian arms dealer Viktor Bout.
Iran is reacting sharply to U.S. Secretary of State Hillary Clinton's remarks that the Persian state is becoming a military dictatorship. Iran's supreme leader, Ayatollah Ali Khamenei, accuses Clinton of spreading "lies" and the United States of turning the region into a so-called "arms depot." But several Washington-based analysts on Iran back Clinton's assertions.
Iran's Revolutionary Guard was formed in 1979 to protect the Ayatollah Ruhollah Khomeini's Islamic Revolution from the Shah's army.
An Afghan-international security force searched a compound outside the town of Waser, in the Washer District of Helmand province after intelligence information indicated militant activity.
The security force detained two insurgents during the search.
As the joint force was leaving, a small team of militants attempted to set up a small-arms ambush. The security force engaged them and killed one insurgent.