Afghan leaders have appeared to accuse Pakistan of harbouring insurgents behind a suicide bombing that killed one of the most powerful men in northern Afghanistan.
The government also said it was investigating whether security forces had been infiltrated.
Dawood Dawood, the north Afghanistan police chief, was killed in yesterday's attack in Takhar province.
Two Afghan police and two German soldiers were also killed, underlining the spread of insurgent violence into once peaceful areas of the country.
"No one in Afghanistan would carry out these attacks. All evidence shows that these operations are planned outside of Afghanistan," Waheed Omer, chief spokesman for President Hamid Karzai, told reporters.
Kabul regularly accuses elements of the Pakistani government of sheltering insurgents and providing safe havens.
Omer said Afghanistan was suffering because of "the hideouts that these terrorists have and the places where they get mobilised, equipped and plan these terrorist attacks."
Despite the presence of up to 150,000 foreign troops, violence in Afghanistan was at its worst last year since US-backed Afghan forces overthrew the Taliban almost a decade ago. This year is following a similar trend.
The loss of a prominent leader like Dawood is a big blow to a force struggling to become more professional ahead of foreign forces handing over security responsibilities starting in July.
Complicating those efforts are the growing number of incidents where "rogue" Afghan police and soldiers, or insurgents who have infiltrated the security forces, have attacked their trainers and government officials.
Omer said it was too early to say if the Takhar attack had been aided by a "rogue" policeman or soldier, but that the evidence was being examined. Local officials said the bomber was wearing a police uniform when he detonated his explosives.
All foreign combat troops are due to leave Afghanistan by the end of 2014.
The governor of Takhar province dismissed allegations "rogue" elements were involved in Saturday's attack in Taloqan, the capital of Takhar. He said intelligence officials knew about the mission and even had the telephone number of the suicide bomber several days before his attack.
"We sadly failed to catch him before he could carry out his mission," governor Abdul Jabar Taqwa, whose face and hand were burnt in the attack, told reporters in Taloqan.
Shopkeepers closed their doors and hung pictures of Dawood as he was buried, and mourners waved black flags in his honour.