Officials say four policemen were killed and three seriously injured Monday when their vehicle hit a landmine near Agadez, in northern Niger.
Officials say the landmine was planted by the ethnic Tuareg rebel group, the Niger Movement for Justice.
The Niger Movement for Justice, known by its French initials MNJ, came to international attention earlier this year after the rebels launched a number of attacks against government and foreign interests in northern Niger.
A previous Tuareg rebellion broke out in Niger in the early 1990s. The rebel group contends that Niger's government has failed to live up to a 1995 peace deal that promised a degree of autonomy for the group.
At least 11 members of the military police have died in similar attacks in the last two months.