(CNN) -- Somali militants accused the nation's transitional government of "baseless propaganda" after officials said the rebel group is on the verge of splitting up.
Government forces have seized more areas in the capital of Mogadishu with the help of African Union troops, officials said in a statement.
"These gains come amidst reports that the Al-Shabaab's second in command has withdrawn his forces from the city as rifts within the extremist group deepen in the wake of the failed Ramadan offensive," a government statement said this week.
The transitional government has expanded the areas it controls in Mogadishu to seven districts that are home to 90 percent of the city's population, according to the government.
But an Al-Shabaab military commander fired back Friday.
Sheikh Mukhtar Robow told reporters in the capital that the group was united, and he declared the militants "remained students" of al Qaeda leader Osama bin Laden.
Officials said this week that a rift between Robow and Al-Shabaab leader Sheikh Abu Zubayr had resulted in Robow withdrawing his troops from the capital.
Robow called reports of discord "baseless propaganda disseminated" by African Union forces and the transitional government. He said the rebels will continue battling government troops and peacekeeping forces.
The African Union Mission in Somalia has been helping government forces fight Al-Shabaab rebels in the country.
The United States considers the group, which is al Qaeda's proxy in the country, a terrorist organization.
Al-Shabaab is waging a war against Somalia's government in an effort to implement a stricter form of Islamic law, or sharia.
Somalia has not had a stable government since 1991, and fighting between the rebels and government troops has escalated the humanitarian crisis in the famine-ravaged country.