Key Pakistan ally China said Monday it was "deeply shocked" by NATO air strikes that left 24 Pakistani soldiers dead and called for an investigation into the incident.
The deadly strikes early Saturday by NATO helicopters and fighter jets have raised tensions between Islamabad and Washington, already running high after the killing in May of Al-Qaeda leader Osama bin Laden by US special forces.
"China is deeply shocked at the incident and expresses strong concerns and deep condolences to the victims in Pakistan," foreign ministry spokesman Hong Lei told a regular news briefing.
"China believes that Pakistan's independent sovereignty and territory should be respected and that this incident should be earnestly investigated and handled in a serious manner."
Washington has already backed a full inquiry into the strikes and expressed condolences.
Nonetheless, hundreds of enraged Pakistanis took to the streets Sunday, burning an effigy of US President Barack Obama and setting fire to American flags across the country of 167 million.
Pakistan, which has denied a report that its own soldiers' fire provoked the strike, has reacted by closing a vital lifeline to the 140,000 foreign troops serving in Afghanistan and ordering a review of its US alliance.
Pakistan's Foreign Minister Hina Rabbani Khar telephoned US Secretary of State Hillary Clinton to convey a "deep sense of rage" as a joint funeral was held for the dead soldiers, their coffins draped in the national flag.
China is the main arms supplier to Pakistan, which sees Beijing as an important counter-balance to its traditional rival India. New Delhi has recently improved its ties with the United States, causing worry in Islamabad.
China and Pakistan conducted joint military exercises over the weekend and Beijing has also built two nuclear power plants in Pakistan and is contracted to construct two more reactors.