NIAMEY, July 20 (Reuters) - Niger's army said three soldiers were killed on Friday when a surveillance patrol ran over a landmine in the desert north, while Tuareg-led rebels said they had killed five troops in an attack in the same area. The Nigerien Armed Forces (FAN) said in a statement that the incident, which left another soldier injured, occurred near the settlement of Abardok, in the isolated north of the landlocked West African state. "The FAN reaffirms that it will retain its presence in the north," said the armed forces statement, which made no reference to the rebel claims. The Nigerians' Movement for Justice (MNJ) said on their Web site, however, that they had killed five soldiers and injured several more in an attack to the east of Abardok. It was not clear if they were referring to the same incident. During its five month old uprising to demand greater control over the region's vast uranium resources, the MNJ has killed at least 33 soldiers and taken dozens hostage. The light-skinned Tuaregs previously rebelled against a black African-dominated government in the 1990s, winning greater autonomy.