Twin explosions in the northeastern Kenyan town of Wajir have killed at least one person and injured at least three others, sources have told Al Jazeera.

The explosion occurred after nightfall at Baraza Park, a Somali-populated district, and the injured were taken to the district hospital.

Police said they suspect that the attack was carried out either using hand-grenades or an improvised explosive device, but added that they could not immediately confirm the type of weapon used.

Police secured the area following the blast, according to the Interior Ministry.

The Somali al-Shabab armed group have carried out several high-profile attacks in Kenya, but are also known to carry out small-scale bombings. On Tuesday, five police officers were killed by al-Shabab gunmen in an ambush while they were on patrol.

The group had said that it was part of an "ongoing war" against Kenya in retaliation for the country having sent troops to fight them in neighbouring Somalia.

The attacks on Kenyan targets began in 2011, after Kenya Defence Forces troops crossed to Somalia to hunt down fighters associated with al-Shabab.

The troops managed to unseat al-Shabab from several strongholds, sparking frequent retaliatory attacks.

Source: Al Jazeera