Pakistani intelligence officials say a U.S. drone strike killed at least 21 militants in the country's North Waziristan tribal region Wednesday.
The officials say two missiles slammed into a compound near Miran Shah, the main town in the tribal area, targeting members of the Haqqani network -- a militant group affiliated with the Taliban and al-Qaida fighting coalition forces in neighboring Afghanistan.
Officials say the dead included Afghan Taliban, as well as some Arabs and Uzbek nationals.
The strike took place just days after Pakistani President Asif Ali Zardari called on the United States to agree on "clear terms of engagement" in the fight against Islamist militants operating in the country.
Washington has been pushing Pakistan to conduct an offensive against Taliban and al-Qaida-linked militants in North Waziristan. Islamabad has resisted, saying it must consolidate military gains made in other areas first.
U.S. officials have never publicly acknowledged the use of drone strikes inside Pakistan, but privately they have confirmed their existence to various news outlets. Pakistan has condemned the attacks as a violation of its sovereignty, but the strikes are believed to be carried out with the help of Pakistani intelligence.
The air strike campaign has intensified since U.S. special forces killed Osama bin Laden in the northern Pakistani city of Abbottabad on May 2. The U.S. raid on bin Laden's compound, conducted without notifying Pakistani authorities, further strained relations between the two countries.
Some information for this report was provided by AP, AFP and Reuters.