Pakistan is denying reports it provoked NATO cross-border airstrikes that killed 24 Pakistani soldiers in an incident that has further strained U.S.-Pakistan relations.

Pakistan's army spokesman Major General Athar Abbas said Monday claims that Pakistani troops initiated the firefight Saturday are not true and that NATO and Afghan officials were “making excuses.” He noted that there were no losses or casualties among coalition troops.

Unnamed Afghan officials said Sunday that NATO and Afghan forces patrolling near the Pakistan border came under fire from the Pakistani base. NATO then called in the coalition airstrikes that killed two dozen Pakistani soldiers in the Mohmand region, near the Afghan border.

NATO and U.S. military officials have offered condolences and pledged a full probe into the incident. A Pentagon spokesman said Monday the U.S. Central Command was dispatching a team to conduct its own investigation.

General Abbas said Monday the Pakistani soldiers were victims of unprovoked aggression and that the Pakistani military responded only after the troops were killed. He said the attack lasted up to two hours.

The Pakistani military spokesman noted that the area had been recently cleared of militants and that Pakistan had provided NATO with the exact locations of the region's two Pakistani military posts named “Volcano” and “Golden.”

Pakistani Prime Minister Yousuf Raza Gilani told CNN on Monday that the U.S.-Pakistani alliance can continue on the basis of mutual respect and mutual interest, but that both were currently lacking. He added that a parliamentary committee will investigate the NATO attack.

The White House said President Barack Obama called Saturday's attack a tragedy. Spokesman Jay Carney told reporters in Washington that the U.S.-Pakistan relationship continues to be very important, cooperative and also “complicated.” He said it is in America's national security interest to maintain a cooperative relationship with Pakistan because both countries have shared interests in the fight against terrorism.

U.S. State Department spokesman Mark Toner said Monday that the United States was concerned about the incident's impact on U.S.-Pakistan relations. He added that it was in Pakistan's best interest to attend the upcoming conference on Afghanistan in Bonn, Germany, amid reports that Pakistan was reconsidering taking part in the summit in light of the NATO airstrike.

Pakistan responded to the airstrikes by shutting down all NATO supply lines through its territory to Afghanistan and ordering the U.S. to vacate an air base in southwestern Baluchistan province within 15 days.

The main Pakistani association that delivers fuel to NATO forces in Afghanistan told VOA on Monday that it will not resume supplies until the Pakistani government guarantees reimbursement for lost income due to the shutdown.

Meanwhile, anti-US demonstrations were held for a second day throughout Pakistan. Protesters in Karachi and other cities called for the Pakistani government to sever its alliance with the United States.

And in Beijing, China's foreign ministry spokesman said Monday that China was “deeply shocked” by the incident and has offered condolences to Pakistan.

Russian Foreign Minister Sergei Lavrov said any violation of a country's sovereignty, even during counter-terrorist operations, is unacceptable. He telephoned his Pakistani counterpart Hina Rabbani Khar on Monday and called for NATO to thoroughly investigate the incident.