The incident in the town of Beni followed a number of overnight raids in the area blamed on the Islamist group ADF-NAUL, who are thought to have massacred more than 100 people this month, using hatchets and machetes to kill their victims.
Witnesses said the man, who has not been identified, aroused suspicion on a bus when passengers discovered he could not speak the local Swahili language and that he was carrying a machete.
Speaking from the town of Beni, Congo's President Joseph Kabila said the ADF-NALU militants would face the same fate as the rebel movement M23, which was defeated by a U.N.-backed government offensive last year.
"There is no question of negotiation with the terrorists," Kabila said in a speech at a local hotel. "They will be defeated as was the case with the M23. And it will be very soon."
ADF-NALU is an alliance of groups opposed to the Ugandan government that has operated from bases in neighboring Congo since the mid-2000s, undermining Kinshasa's grip on the area.
The movement was blamed for the deaths of 14 people, killed early on Thursday in the village of Kampi ya Chui, bringing the total death toll this month to at least 107, said Teddy Kataliko, president of the Civil Society of Beni.
Tensions ran high in the town on Friday morning with around 100 demonstrators blocking the road from the airport into town, throwing stones and waving machetes to demand greater government protection against the rebels.
Local government officials could not immediately be reached for comment. Earlier in the week, the government sought to downplay the threat posed by the group, which it had previously said was defeated in an operation earlier this year.
Estimates of its strength vary greatly, but the website of the U.N.'s peacekeeping mission in Congo estimates it has around 500 fighters.
The Ugandan government has said ADF-NALU is allied with Somalia's al Qaeda-linked al Shabaab movement, but analysts say the nature of these ties is not clear, despite the ADF-NALU's clear Islamist ideology.In his speech on Friday, Kabila appealed for public support for a ramping up of its offensive against the group, but did not specify what that would entail.
"I call on the population to support the army because the victory against the M23 was because the population was behind the army," he said. "I call on young people to join the army in great numbers."
Kabila also defended the U.N. peacekeeping mission known as MONUSCO following criticism from locals that it had failed to defend them and had even collaborated with ADF-NALU.
Crowds of mainly young men attacked several peacekeeping facilities with stones and bows and arrows last week, forcing the evacuation of some staff.
The U.N. mission says it has stepped up patrols in the area in the wake of the massacres.