A second raid on NATO convoys in Pakistan has left two people dead. Earlier, suspected militants torched 27 tankers carrying fuel for NATO troops stationed in Afghanistan.
The attacks came a day after Pakistan denied the alliance access to a vital border crossing.
The move comes in response to a NATO air strike that killed three Pakistani soldiers, allegedly by accident.
Islamabad says it will consider harsher measures if alliance forces continue incursions into its territory.
US-led strikes against alleged militants in Pakistan have been taking place for years.
At the same time, Islamabad is hailed by Washington as a vital non-NATO ally in the war on terror.
Former Pakistani president Pervez Musharraf says the war cannot be won without Islamabad's support.
“Unless Pakistan is a part of the fight against terrorism and extremism, the fight cannot succeed,” Musharraf said. “Therefore, it is incumbent on all on US and allied forces to be conscious of the sensitivities of Pakistan and then take actions. No violation of the sovereignty of Pakistan can be accepted by anyone in Pakistan.”