Pakistan's military says a transport helicopter has crashed because of a technical failure, killing 26 security personnel on board.

Officials say investigators are looking into the incident, which occurred Friday outside Peshawar, the main city in the northwest.

Earlier Friday, Pakistani intelligence officials said a suspected U.S. drone fired missiles on a militant training center in the South Waziristan tribal region, killing at least 10 people.

Pakistani military forces and suspected U.S. drone strikes regularly target areas controlled by Baitullah Mehsud, a top Taliban leader and al-Qaida ally wanted by both Pakistan and the United States.  Pakistani troops are preparing for a ground offensive against Mehsud and his Taliban allies.

The stepped-up campaign in western Pakistan comes as troops also continue to clear the greater Swat Valley region of militants allied with another Taliban faction.  Pakistan's army says troops in that area killed 13 suspected militants and arrested 24 others in the most recent operation.

In other news, the United Nations Children's Fund says it is deeply concerned about the condition of hundreds of thousands of children who are among the two million people who have been displaced in Pakistan by the violence.

UNICEF says nearly half of those people are believed to be children and many are in urgent need of health and educational services, nutritional support, access to clean water and sanitation, as well as protection.

Some information for this report was provided by AP and Reuters.