At least 29 people have been killed in two shootings in the Kenyan coastal district of Lamu.

Witnesses said about a dozen men opened fire in the trading centre in Hindi, Lamu County late on Saturday evening, killing nine people including a police officer.

'They went around shooting at people and villages indiscriminately,' area chief Abdallah Shahasi told Reuters.

A further 20 people were killed in a separate attack in the Gamba region of Tana River County. The Somalian al-Qaida-linked group al-Shabaab have reportedly claimed responsibility for the attacks.

County commissioner Miiri Njenga said some government offices and properties were also burned down. The Kenya National Disaster Operation Centre said on Twitter that it is responding to the attacks.

Last month, at least 60 people were killed in Lamu after gunmen launched attacks on hotels and a police station.

Witnesses told the Daily Telegraph that the alleged al-Shabaab operation was spearheaded by a white man who speaks 'fluent British English'.

Mpeketoni resident Mary Gachoki said: 'I saw a white man who was speaking in fluent British English commanding the rest of the attackers.'

Another witness, who spoke on condition of anonymity, added: 'There was a white man among them. He was commanding them and was shouting now and then.

'I saw him ordering them to carry out the attacks. He could be heard speaking frequently and at one point, he spoke in Arabic, but most of the time in English.'

Five people died in a later attack by an armed gang in the village of Witu, located about 15km (nine miles) from Mpeketoni. Authorities said they arrested 13 alleged separatists accused of planning further coordinated attacks on the coast.

Last September, militants besieged the upscale Westgate shopping mall in Kenya's capital Nairobi, killing at least 67 people and wounding 175.

A series of gun and grenade attacks in Nairobi and along Kenya's coast have destabilised the country since Kenyan troops went into Somalia in October 2011 to fight al-Shabaab.