The Somali-led Al-Qaeda branch staged an attack against police in the tense border region late Monday, claiming they had killed 20 police in a bomb attack followed by an ambush close to the village of Yumbis, about 80 kilometres (50 miles) northeast of Garissa town.
But Kenyan police said in a statement that only one officer died and four others were wounded, with Interior Minister Joseph Nkaissery dismissing claims of numerous fatalities as "propaganda".
"All officers have been accounted for following the ambush by the terrorists," he said, confirming that one officer had died from his injuries and four others had been wounded.
The attack came just days after extra Kenyan security forces were deployed in the area to strengthen security after a series of raids by the Shebab.
Garissa County has remained volatile with numerous attacks since last month, when four Shebab militants stormed Garissa University College, killing 142 students and six members of the security forces during a day-long siege on the eve of the Easter weekend.