A Japanese travel company took about a dozen tourists to northern Niger in February despite a government request not to enter the area due to Islamist militant activity, a senior Foreign Ministry official said.

All of the tourists returned safely from the two-week tour.

Even so, the official described the sightseeing trip into the area, which was subject to an evacuation advisory, as "incomprehensible."

The Foreign Ministry has four levels of travel advice. An evacuation advisory is the highest level of warning. However, advisories are not legally binding.

The ministry learned in January that the tour planned to visit mountains and deserts in the region for about two weeks and asked the travel agency to cancel it.

But the company refused, saying "the military will be involved in guiding and the safety measures are sufficient."

The official said the ministry did not confiscate the tourists' passports to prevent travel because "Niger is not as risky for Japanese people" as northern Syria, where the Islamic State militant group is active.

In February, the ministry stopped a Japanese freelance photographer from traveling to Syria by confiscating his passport, the first time it has taken such a step.

The ministry asked the government of Niger to enhance security while the tourists were in the country. Boko Haram militants have been conducting a series of attacks in Niger since February.