Somali militants known as al-Shabab have killed some 36 quarry workers near the north Kenyan town of Mandera, police say.
The attackers separated Muslims from non-Muslims and shot the Christians dead, the BBC quoted residents said.
Earlier, one person was killed in a bar popular with non-Muslims in a neighboring district.
Al-Shabab said it carried out the attack, blaming the involvement of Kenyan forces in Somalia “and their ongoing atrocities therein, such as the recent air strikes on Muslims”. The group put the number of killed at 40, higher than official accounts.
Al-Shabab killed 28 people in an attack on a bus targeting non-Muslims in the same area last week.
The recent attack took place at the quarry in Kormey, 15km (nine miles) from Mandera town early on Tuesday. Witnesses said the victims were caught after midnight, while sleeping in their tents at the quarry.
Reuters news agency quoted one witness as saying that most of the victims had been shot in the head, and four had been beheaded.
In the attack on a bar in the town of Wajir earlier on Monday night, gunmen reportedly opened fire and hurled grenades, killing one and injuring 12.
Mandera County borders both Somalia and Ethiopia, and it is dominated by Somalis, who are largely Muslims.
Many of the quarry workers killed are reported to have come from the south of the country where Christians predominate.
Al-Shabab has stepped up its campaign in Kenya since 2011, when Kenya sent troops across the border to help battle the militants.
In one of the worst attacks on Kenyan soil, 67 people were killed last year when four gunmen took over the Westgate shopping mall in Nairobi.
More recently, dozens of people were killed in a series of shooting attacks in Kenya’s coastal districts.
The security situation has led to calls from the opposition and some in the governing party to call for the dismissal of Interior Minister Joseph Ole Lenku and police chief David Kimaiyo.
