Islamabad:  The NATO air strikes on Pakistani checkposts were an 'unprovoked act of blatant aggression' as the coalition was informed that it was an army check-post that was being attacked, a top Pakistani army official said.

The NATO-led International Security Assistance Force (ISAF), even after being informed, after the strike on the first border post, returned with helicopter gunships to strike at a second post, Director General of Military Operations Maj. Gen. Ishfaq Nadeem was quoted as saying by the Associated Press of Pakistan.

The Nov 26 attack on the two army check-posts left 24 Pakistani soldiers dead, sparking outrage in the country and straining relations with the US.

Nadeem said that in the attacks all coordination procedures were violated.

'The positions of the posts were already conveyed to the ISAF through map references and it was impossible that they did not know these to be our posts,' he said at the army general headquarters in Rawalpindi.

Giving details of the incident, Nadeem said that just after midnight two to three NATO helicopters appeared and started engaging the Volcano border post, breaking down all communication systems.

In response, the Boulder border post engaged the NATO helicopters with anti-aircraft guns and all available weapons.

'We informed them about the attack. But, the helicopters reappeared and also engaged the Boulder post,' Nadeem said.

He said there were four border communication centres to coordinate operations against militants but all Standard Operating Procedures (SOPs) were violated by ISAF and NATO on the night of the attack.

The area where the attacks were carried out was already cleared of militants by Pakistani forces and there was no cross-border movement of terrorists from Pakistan to Afghan territory, he said.

Nadeem said prior to this incident, there had been three attacks which were carried out from across the border in 2008, 2010 and 2011, killing 14 Pakistani soldiers and injuring 13.

'No information regarding inquiry of these attacks was shared or provided to us despite our repeated requests and when provided, it was inaccurate and incomplete,' he said.