NAIROBI: Somali Islamist terrorists said they destroyed seven aircraft and three vehicles on Sunday in an attack on a military base in Kenya's Lamu county used by both US and Kenyan troops, although their account could not be independently verified.

In a statement, the al-Shabaab group said the attack, launched at dawn, was continuing hours later and said their fighters were engaging US troops in close-quarters combat.

"Seven aircraft and three military vehicles were destroyed in the attack," said the statement, which included photos of aircraft ablaze and an al-Shabaab militant standing nearby.

In a tweet, the US Africa Command confirmed an attack on the Manda Bay Airfield had occurred. It said it was monitoring the situation and would provide an update "as facts and details emerge".

Kenya sent troops into Somalia in 2011 after a spate of cross-border attacks and kidnappings. They were later absorbed into an African Union peacekeeping force, now 21,000-strong, that supports the shaky, Western-backed Somali government against which al-Shabaab has waged a protracted insurgency.