Suspected al-Shabaab fighters killed 14 sleeping quarry workers and wounded many others in a gun and grenade attack in northern Kenya staged only weeks before a highly anticipated visit by President Obama to the East African country.

The gunmen raided the remote village of Soko Mbuzi near the Somalia border at around 1am Tuesday, smashed through a gate using a petrol bomb before hurling grenades at the workers and spraying those who tried to flee with bullets.

Local police chiefs said the attack bore all the hallmarks of the Somalia-based al-Qaida affiliate which has been blamed for a series of atrocities in East Africa.

"All indications are that they were al-Shabaab militants. They destroyed metal grilled doors before they bombed the houses and opened fire on the innocent victims,” Mandera County Commissioner Alex Ole Nkoyo told The Standard newspaper.

Several victims were rushed to hospital although the exact number of those affected were unclear.

The killings follow a pattern where al-Shabaab militants have targeted non-locals working in the predominantly Muslim region near the Kenyan-Somalia border. Workers from areas outside the region tend to be Christian.

In December, 36 quarry workers were killed in similar circumstances in the same county.

Kenya has been on a heightened state of alert since it was announced in March that Obama will tour the country at the end of July to attend a global entrepreneurship summit.

Although the visit has generated considerable enthusiasm, in part due to the fact Obama’s father was Kenyan, there are concerns that militants could take advantage of the occasion to stage attacks.

Hundreds of security officers have been mobilised to bolster security and surveillance cameras have been installed in many streets in the capital Nairobi. But al-Shabaab have shown themselves capable of operating at will in the vast, historically marginalised region near the Somalia border where they are most active.

After a particularly shocking shooting rampage in a university in the northern town of Garissa left 148 students and security students dead in April, Obama called his Kenyan counterpart Uhuru Kenyatta to offer his support and said he would not change his plans to visit the country.

The Kenyatta government, which has come under severe public pressure to contain the al-Shabaab attacks, is expected to find itself under increasing scrutiny in the weeks leading up to Obama’s visit.