ISLAMABAD (AP) — The head of the United Nations has said during a visit to Pakistan that drone strikes must comply with international law.

Ban Ki Moon did not specifically mention Tuesday whether or not he thought U.S. strikes in Pakistan were in compliance.

But a U.N. official investigating the impact of drones, Ben Emmerson, said in March that the attacks contravene international law because they violate Pakistan's sovereignty.

President Barack Obama has said the strikes comply with international law.

Pakistani officials regularly condemn the strikes as a violation of the country's sovereignty and international law. But the government is known to have supported some of the attacks in secret in the past, and U.S. officials insist the country's powerful army still does.

The Pakistani army denies the allegation.