WASHINGTON  Since the suicide bombing that took the lives of seven Americans in Afghanistan on Dec. 30, the Central Intelligence Agency has struck back against militants in Pakistan with the most intensive series of missile strikes from drone aircraft since the covert program began.

Beginning the day after the attack on a C.I.A. base in Khost, Afghanistan, the agency has carried out 11 strikes that have killed about 90 people suspected of being militants, according to Pakistani news reports, which make almost no mention of civilian casualties. The assault has included strikes on a mud fortress in North Waziristan on Jan. 6 that killed 17 people and a volley of missiles on a compound in South Waziristan last Sunday that killed at least 20.

“For the C.I.A., there is certainly an element of wanting to show that they can hit back,” said Bill Roggio, editor of The Long War Journal, an online publication that tracks the C.I.A.’s drone campaign. Mr. Roggio, as well as Pakistani and American intelligence officials, said many of the recent strikes had focused on the Pakistani Taliban and its leader, Hakimullah Mehsud, who claimed responsibility for the Khost bombing.

The Khost attack cost the agency dearly, taking the lives of the most experienced analysts of Al Qaeda whose intelligence helped guide the drone attacks. Yet the agency has responded by redoubling its assault. Drone strikes have come roughly every other day this month, up from about once a week last year and the most furious pace since the drone campaign began in earnest in the summer of 2008.