Kenya's military has struck al Shabaab targets in one of the most devastating attacks against the al Qaeda-linked insurgents since it launched an operation in Somalia to crush the rebels last October, a Kenyan army officer said on Saturday.

Colonel Cyrus Oguna said two helicopter gunships hit a convoy of al Shabaab in Dalayat village in southern Somalia on Friday evening, following intelligence that the fighters were planning to attack Kenyan forces in nearby Bhadhadhe.

This is one of the best attacks yet ever because we got them in their vehicles before they could disembark. Several al Shabaab were killed and many more injured, Oguna told a news conference.

Kenya began its military campaign against the rebels in southern Somalia after a series of cross-border raids by al Shabaab against targets on Kenyan soil, which threatened the east African nation's tourism business.

Oguna said nine vehicles mounted with weapons, known locally as Technicals, and nine lorries were destroyed in the attack. There were no Kenyan casualties, he said.

Emmanuel Chirchir, the military spokesman, said the force estimated that more than 100 al Shabaab fighters were killed in the attack.

Al Shabaab dismissed the claims as propaganda.

Kenya has not destroyed or even attacked al Shabaab strongholds. It is propaganda Sheikh Abdiasis Abu Musab, al Shabaab's spokesman, told Reuters.

Oguna said the capture of Bhadhadhe and Hosungow town, which was also taken last week, would remove sources of revenue for the rebels because they were used for trafficking goods.

We expect to see more ground being ceded by al Shabaab because they are weakened, he said.

The campaign against the rebels in the south, together with another by an African Union force in the capital Mogadishu, are aimed at stabilising Somalia after two decades without an effective central government.

(Reporting by Duncan Miriri; Additional reporting by Feisal Omar in Mogadishu, Editing by Rosalind Russell)