At least three people have been killed in a fresh cross-border attack by Somalia-based Takfiri al-Shabab militant group in the troubled northeast of Kenya, security sources say.

The casualties were caused late Saturday after a group of gunmen opened fire in a residential area of northeastern Wajir county, close to the border with Somalia, Samuel Mukindia, a regional police commander, said on Sunday.

The police official added that at least two men and a women were killed in the deadly incident.

Mukindia noted that the assailants immediately escaped and fled to the other side of the porous border following the raid.

According to local residents, the real target of the attackers is believed to have been a local administrator, who lives close to the scene of the attack.

"The attackers were possibly heading to the chief's residence, but since they were not familiar with the house, they started shooting people indiscriminately," media outlets quoted Ahmed Muhamed, an elder in Wajir as saying.

Local sources say the administrator is an outspoken critic of the militant group.

The latest attack comes as Wajir, located 490 kilometers northeast of the Kenyan capital Nairobi, has come under several attacks by the militant group in recent months.

Kenyan border regions of Mandera County and Garissa County have been hit by an upsurge of attacks by the al-Qaeda-linked Shabab militants.

In early April, al-Shabab carried out an attack against the Garissa University College campus, killing nearly 150 and injuring 79.

The militant group has vowed to continue attacks until Kenya pulls its troops out of Somalia.

The government in Nairobi sent over 3,000 soldiers to Somalia in late 2011, after the militant group carried out a series of raids inside Kenya.

Somalia has been the scene of fierce fighting between al-Shabab militants and government forces since 2006.

The militant group has been pushed out of the Somali capital, Mogadishu, and other major cities in the country by the African Union Mission in Somalia.

The al-Qaeda linked group has, however, continued to launch attacks in Mogadishu despite being ousted from its bases in the seaside city in 2011.