KABUL (BLOOMBERG) - The Taliban will officially recruit suicide bombers to become part of the army as the militant group tries to contain its biggest security threat from rival Islamic State of Iraq and Syria (ISIS) since forming the government in Afghanistan four months ago.

Before sweeping into power last year, the Taliban used suicide bombers as a key weapon to attack and defeat US and Afghan troops in the 20-year war.

Now the group wants to reform and organise the scattered squads of suicide bombers across the country to operate under a single unit and protect Afghanistan, said Taliban deputy spokesman Bilal Karimi.

Its main target now would be the local offshoot of ISIS, which has carried out at least five major attacks as the Taliban looked to consolidate power after the United States withdrew from Afghanistan last August.

Several of those attacks were carried out by suicide bombers.

"The special forces that include martyrdom seekers will be used for more sophisticated and special operations," Mr Karimi said by phone, without providing details.

The militant group is building a "strong and organised army to bolster defence" nationwide and at the borders, with the suicide bombers becoming a integral part of the strategy, Mr Karimi added.

Some 150,000 fighters will be invited to join the military, Al Jazeera reported in November, citing the Taliban chief of staff Qari Fasihuddin.

The recruitment drive comes after the Taliban purged the military ranks to stop those who were conducting house-to-house searches to settle scores with opponents, according to spokesman Zabihullah Mujahid.

The group also said it had begun to identify and capture possible ISIS infiltrators within its own ranks.

ISIS fighters have constantly challenged the authority of the Taliban, prompting concerns that Afghanistan could descend into another war.

The group's deadliest attack took place on Aug 26 when a suicide bomber killed nearly 200 people, including 13 US marines, in Kabul airport as desperate Afghans were waiting for US evacuation flights to flee the country.