Saeed Ansari, an NDS spokesman, said: "Live coverage does not benefit the government, but benefits the enemies of Afghanistan".
And, voicing its support for the decision, Hakim Ashir, the head of the Government Media and Information Centre, said: "Journalists are going to the scene of ongoing attacks, they endanger themselves.
"But they also help inform the enemy with their live broadcasts or reporting of the progress of [police] operations."
The move was denounced by Afghan journalists and rights groups, who claim it will deprive the public of vital information about the security situation during attacks.
"Such a decision prevents the public from receiving accurate information on any occurence," Abdul Hameed Mubarez, the head of the Afghan National Media Union, said.
"The government should not hide their inabilities by barring media from covering incidents," Laila Noori, who monitors media issues for Afghanistan Rights Monitor, the country's main liberties watchdog said.
"People want to know all the facts on the ground whenever security incidents take place."
No formal restrictions
The Afghan government banned reporting violence for a single day during a presidential election last year, but otherwise had not had formal restrictions on filming security incidents.
However, journalists have occasionally been beaten by security forces while filming at the scene of incidents in the past.
The announcement of the ban came on the same day that the Nato-led International Security Assistance Force (Isaf) reported six of its service members had been killed in various attacks fighting the Taliban.
Isaf troops launched an offensive last month to drive the Taliban out of their strongholds as part of a plan to hand control of the country to Afghan forces before a planned US troop drawdown that is scheduled to begin in July 2011.