An unknown number of insurgents were killed in fighting between Kenyan Defense Forces and al-Shabaab guerrillas in the Kenyan border town of Hulugho, local officials said.

Garissa County Commissioner Rashid Khator said the militants were attempting to cross the Kenyan border into Somalia when the encounter took place, and police suspected the men had been involved in an attack on an administration police camp at Galmagala, where four police officers were killed, The Star newspaper reported Wednesday.

"We believe that these are the same individuals who were involved in the killings of the officers. KDF officers engaged them in a heavy exchange of fire and gunned down several of them," Khator told reporters.

Khator said the estimated 20 al-Shabaab militiamen were said to be wearing camouflage uniforms similar to those of the Somalia Transitional Federal Forces, and that KDF and other Kenyan security have begun operations along Kenya's border towns in an effort to apprehend the men.

Al-Shabaab has been waging a war in Somalia for nearly a decade and its activities have crossed Somalia's borders, prompting Kenya and Uganda to send African Union Mission in Somalia troops to contain the threat. The AMISOM peacekeeping forces eventually forced al-Shabaab to abandon its positions in the Somali capital Mogadishu and other Somali cities, including Kismayo.

Western governments remain concerned about al-Shabaab, as in February 2012, al-Shabaab's emir in Somalia and al-Qaeda leader Ayman al-Zawahiri released a joint video to formally announce a merger of the two organizations. While al-Shabaab has capabilities to conduct attacks elsewhere in East Africa -- notably a 2010 bombing in Uganda and the issuance of threats against both Kenya and Burundi -- its attacks have primarily focused on targets inside Somalia. Despite the merger with al-Qaida, al-Shabaab's leaders prioritize the creation of an Islamic state in Somalia, rather than embracing al-Qaida's emphasis on external attacks. In February 2008 the U.S. State Department designated "al-Shabaab, aka al-Shabab, aka Shabaab, aka the Youth, aka Mujahidin Al-Shabaab Movement, aka Mujahideen Youth Movement, aka Mujahidin Youth Movement, aka MYM, aka Harakat Shabab al-Mujahidin, aka Hizbul Shabaab, aka Hisb'ul Shabaab, aka al-Shabaab al-Islamiya, aka Youth Wing, aka al-Shabaab al-Islaam, aka al-Shabaab al-Jihaad, aka the Unity of Islamic Youth" as a "Specially Designated Global Terrorist" organization.

Al-Shabaab's operational leader Ahmed Godane stated in a recent audio message he is determined to reform the organization's structure to cope with changing operational parameters, and to inculcate a new, younger generation that can interact with the rapidly changing global requirements of jihadi conflict, including a new generation of recruits with Western exposure, who understand Western values and vulnerabilities and speak their languages.

Al-Shabaab's new operational tactics appeared in its propaganda video, "The Path to Paradise: From the Twin Cities to the Land of Migration," part of al-Qaida's propaganda outreach to the next generation, which featured three young Somali-Americans who migrated from the United States to fight jihad in Somalia.

Despite AMISOM's military successes, the Somali government in Mogadishu, backed by the Britain and the U.S., remains institutionally weak, providing a potential area for al-Shabaab's re-emergence.