At least 29 people were killed when attackers wielding guns raided two separate areas on the Kenyan coast overnight, the Kenyan Red Cross has said.

Four people died at Hindi trading centre in Lamu county, near the scene of attacks in which 65 people were killed last month, the Red Cross said on Twitter. Nine more were killed in another attack in the Gamba area of Tana River county.

Kenya's National Disaster Operations Centre had said in a brief statement on Twitter late on Saturday that gunfire had broken out.

A spokesman for Somalia's al-Shabab armed group issued a statement late on Saturday claiming that its fighters had carried out an attack in the area.

"The attackers came back home safely to their base," al-Shabab's military spokesman Abdulaziz Abu Musab said, claiming that at least 10 people had been killed in the attack.

The incident took place around 15km from Lamu, once a popular tourist resort.

Previous attack

Al-Shabab claimed responsibility for last month's attack at Mpeketoni, saying it was in retaliation for Kenya's military presence in Somalia as part of the African Union force backing the country's fragile and internationally-backed government.

Survivors of the attack on the town and a similar attack the following night in a nearby village reported gunmen speaking Somali and carrying al-Shabab flags killed non-Muslims and said their actions were revenge for Kenya's military presence in Somalia as part of the African Union force fighting the group.

Kenya's president, Uhuru Kenyatta, however, denied that al-Shabab were involved and instead blamed "local political networks" and said that the victims had been singled out because of their ethnicity.

The attackers appeared to target Mpeketoni because the town is a mainly Christian settlement in the Muslim-majority coastal region, having been settled decades ago by the Kikuyu people, the same tribe as Kenyatta.

Police also arrested alleged separatists from the Mombasa Republican Council, a group that campaigns for independence of the coastal region, as well as the governor of Lamu county, who is an opposition politician.

The unrest in the coastal region has badly dented Kenya's tourist industry - a key foreign currency earner and massive employer for the country - at one of its traditionally busiest times of the year.