Pakistan has voiced anger at Nato-led raids against insurgents which crossed over its border from Afghanistan.
Apache helicopters are said to have taken part in the operations at the weekend which killed 50 insurgents.
Pakistan’s Ministry of Foreign Affairs said the raids were a clear violation of sovereignty.
But the BBC’s Adam Mynott in Islamabad says the comments were mainly aimed at a domestic audience, among which US military activity is often unpopular.
The Nato-led International Security Assistance Force (Isaf) said it had crossed over the border into Pakistan after coming under fire in the Khost region of Afghanistan. It said 49 insurgents had been killed.
On Saturday, two Apache helicopters came under small-arms fire from the same area and again crossed the border, killing four to six insurgents, said Isaf.
In the statement, Pakistani officials said the incidents had been “a clear violation and breach of the UN mandate under which Isaf operates”.
It said the mandate ended at the Afghan border and there were “no agreed ‘hot pursuit’ rules” allowing Isaf troops to cross the border.
“Any impression to the contrary is not factually correct. Such violations are unacceptable,” said the statement.
“In the absence of immediate corrective measures, Pakistan will be constrained to consider response options.”
The Pakistan government backs much of the military action taking place against insurgents operating around the border region in Afghanistan, says our correspondent.
So the strong statement is largely directed at a domestic audience in Pakistan, he adds, among whom anti-American sentiment has been fuelled by the escalating numbers of drone attacks on targets in the country.
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