Tunisian security forces dismantled a bomb found near the home of a military colonel on Friday, witnesses said, the third bomb scare to be reported in the same day.
Security forces have declined to officially comment on the incident, but some said privately that Islamist militants appear to be launching an intensified campaign against Tunisian security forces.
"I think the terrorists are trying to send a message to the army and security forces," a policeman near the site of the dismantled bomb said. "We've received the message and we're going to defend our nation from them, and they will not succeed."
On Monday, Islamist militants ambushed and killed eight soldiers in a remote region near the Algerian border, in one of the deadliest attacks in decades.
The assault followed two bomb attacks near security forces in Tunis, the first time the capital has suffered such attacks. No one was hurt.
The North African country is now struggling to combat rising instability amid a growing political crisis, as the secular opposition tries to oust the moderate Islamist-led government.
Tunisian forces also on Friday launched a heavy ground and air strike campaign on militants at Mount Chaambi near the Algerian border, a remote area where the army has been hunting Islamist militants since December.
Residents of the wealthy Menzah 9 district in Tunis said they had seen two men on a motorbike place a box near the house of a general next door and immediately phoned the police.
A Reuters reporter in the area saw policemen with dogs imposing a security cordon before dismantling the bomb.
"The box had a battery, a cord, and a letter in it. The police took the box away after dismantling the bomb," a resident said.
Earlier on Friday, a man in a neighbourhood 10 kilometres (6.3 miles) north of the capital was killed when he accidentally blew himself up preparing a bomb. Another man in a nearby suburb blew off his own hand as he prepared an explosive device. He was arrested and taken to hospital.
Security forces around the capital appeared to be on high alert, setting up checkpoints on several main streets around the capital.