Islamist militants set off several explosions in the Somali capital on Sunday, their spokesman said, demonstrating the rebels' ability to attack the heart of government-controlled areas despite security gains, Reuters reported.

The guerilla-style attacks were typical of al Shabaab rebels who have waged a six-year campaign to impose their strict interpretation of Islamic law on the country.

The militants had fired five mortar shells and hurled several grenades, wounding at least two women, senior police officer Abdiqadir Mohamud said.

Somali security forces responded with volleys of gunfire, witnesses said. Casualty numbers were thought to be low.

Al Shabaab said late last month the rise in coordinated attacks conducted by its fighters pointed to its enduring strength and at the time warned of more attacks in Ramadan.

The African Union peacekeeping force, known as AMISOM, has struggled to control areas won back from al Shabaab. The central government extends little influence beyond the capital where security has improved since peacekeepers flushed the militants out of their bases two years ago.