Afghanistan has cancelled a military trip to Pakistan due to "unacceptable Pakistani shelling" of the country's mountainous eastern borderlands, the foreign ministry said on Wednesday.
More than two dozen Pakistani artillery shells were fired into Afghanistan's eastern province of Kunar on March 25 and 26. The cancellation of the trip and days of angry diplomatic exchanges have placed further strain on an already fraught relationship.
Eleven Afghan National Army (ANA) officers had been due to take part in a simulated military exercise at the Staff College in the western city of Quetta, gripped by recent sectarian violence directed at Shi'ite Muslims.
"This visit will no longer take place due to the resumption of unacceptable Pakistani artillery shelling against different parts of Kunar province from across the Durand Line on Monday and Tuesday," the ministry statement said.
The Durand Line is the 1893 British-mandated border between the two countries, recognised by Pakistan but not by Afghanistan.
Pakistani support for the Afghan peace process is considered essential because of the two countries' long, porous border and Pakistan's history of supporting militant groups.
The neighbours have engaged in days of of angry accusations, including a Pakistani official denouncing Afghan president Hamid Karzai as an obstacle to peace and saying he was taking his country "straight to hell".
The Afghan government responded by saying "such comments from irresponsible individuals are part of a failed propaganda attempt to undermine the ongoing historic process of transition".
Pakistan has accused Afghanistan of giving safe haven to militants on the Afghan side of the border, particularly in Kunar province, leaving Pakistan vulnerable to counter-attack when it chases them out of its own ethnic Pashtun tribal areas.
Afghanistan sent additional troops and long-range artillery to the border with Pakistan in September last year as tensions rose over a spate of cross-border shelling which killed dozens of Afghan civilians.