Pakistan has imposed new travel restrictions on U.S. diplomats living in the country, the latest sign of worsening ties between the troubled allies since the U.S. raid that killed former al-Qaida chief Osama bin Laden earlier this year.

Diplomatic sources on Sunday said the U.S. embassy in Islamabad received a letter from the Pakistani Foreign Ministry last month setting new limitations on when and how diplomats can move outside the capital. The Associated Press, which obtained a copy of the letter, says the communique requires all U.S. diplomats to apply for special permission to leave the city five days in advance.

Pakistani media report that U.S. envoys travelling from Islamabad earlier this month were turned away from the northwestern city of Peshawar for not having a “no objection certificate” from authorities.

Both governments moved to curb any public disagreement after the restrictions were reported in Pakistani newspapers Sunday. Embassy spokesman Alberto Rodriguez said the U.S. is working with local authorities to resolve the issue.

Pakistan's Foreign Ministry said “no U.S.-specific restrictions have been applied” on diplomatic travel, but added there is a “constructive engagement” under way with the U.S. Embassy about this.

Pakistan reacted angrily to the May 2 bin Laden raid deep inside its territory because it was carried out with no warning to officials in Islamabad. Tensions already were high after a CIA contractor killed two Pakistanis in January.

The U.S. recently suspended about one-third of its $2.7 billion annual defense aid to Pakistan in a show of displeasure at a number of bilateral conflicts.

Despite the tensions, both sides have sought to prevent a breakdown in relations.