Afghan Taliban spring offensive
Afghan security forces are struggling to contain the growing attacks of Taliban insurgentsOmar Sobhani/Reuters

The Afghan Taliban has launched its annual spring offensive in the strife-torn country. This year's offensive has been codenamed "Operation Omari" after the organisation's founder Mullah Mohammad Omar, whose death was announced in 2015.

The Islamist insurgent group said its offensive will be directed at American and Nato forces for the 15th consecutive year. Just hours before the formal declaration by the militant group, there were attacks in Kabul and Nangarhar province.

A statement sent out to media by the extremist group reads: "Jihad against the aggressive and usurping infidel army is a holy obligation upon our necks and our only recourse for re-establishing an Islamic system and regaining our independence."

It added: "The present operation will also employ all means at our disposal to bog the enemy down in a war of attrition that lowers the morale of the foreign invaders and their internal armed militias."

The Taliban announcement comes alongside the reconciliation efforts which are taking place between Afghan government leaders and Taliban representatives. The quadrilateral talks, which are primarily coordinated by Pakistan, involve members of the US as well.

Taliban leader Mullah Akhtar Mansour has cemented his total control over the fractious Islamist movement in order to prepare for "decisive" battles during the spring offensive. The group has promised to make 2016 bloodier than the previous year, when as many as 11,000 civilians were killed.

Days before the Taliban announcement, Mansour told his followers: "Let's prepare for decisive strikes against the enemy purely for the sake of Allah with strong determination and high spirits," according to the group's official website.

Afghan security forces are already struggling to contain Taliban attacks in the wake of foreign troops' withdrawal from Afghanistan. It is estimated the Afghan government controls only 70% of its territory while the rest of the area is in the hands of extremist forces.