An Afghan policewoman has shot and killed a US security adviser in the Kabul police headquarters, NATO and local officials say.
A senior police official told Al Jazeera that the shooting occurred at 10:15am local time (05:45 GMT) on Monday.
The policewoman approached the adviser as he was walking in the heavily guarded police chief's compound in a bustling area of the capital. She then drew a pistol and shot him once, a senior police official told the Reuters news agency.
The woman, a member of the police's gender equality team, is in custody, officials said. Mohammad Daoud Amin, Kabul's deputy police chief, said an investigation is under way to determine whether the killing was intentional or accidental.
Amin said Nargis, a mother of four, had worked with a human rights department of the police for two years and had earlier been a refugee in Pakistan and Iran. She could enter the compound armed because as a police officer she was licensed to carry a pistol, he said.
Mohammad Zahir, head of the police criminal investigation department, described the incident as an "insider attack", in which Afghan forces turn their weapons on US-led coalition troops they are supposed to be working with.
If confirmed to be such an attack, the shooting would be the first time that a female member of Afghanistan's security forces has turned her weapon on a member of NATO's International Security Assistance Force (ISAF) or a foreign contractor.
In an interview with Al Jazeera, Fahim Dashty, chief editor of the Kabul Weekly, said that the attacks could mean the Taliban's presence within the Afghan security forces may be "much wider and strong".
Afghan police killed
Meanwhile, local officials in Jawzjan province said five Afghan local police were killed in a separate insider attack late on Sunday night at a checkpoint in Qush Tepa district.
The attacker then stole his colleague's weapons and fled to join the Taliban, said Faqir Mohammad Jawzjani, the deputy provincial governor.
At least 62 international troops and advisers have been killed in 47 incidents by Afghan soldiers or police this year. NATO forces, due to mostly withdraw from the country by 2014, have speeded up efforts to train and advise Afghan military and police units before the pullout.
"Afghans have borne the brunt of insider attacks, and while the interior ministry does not provide exact statistics on such attacks, the number of Afghan security personnel killed in insider attacks is believed to be at least triple that of the number of foreigners killed," reported Al Jazeera's Jennifer Glasse in Kabul.
"For NATO these insider attacks are of great concern, because the crux of their exit strategy has been training the Afghan security forces and building capacity, but as they withdraw, they rely increasingly on smaller teams, on these contractors [...] to help the Afghans stay on the right track.
"An attack like this inside police headquarters in the centre of Kabul isn't going to do anything to help those efforts."
NATO says about 25 percent of the attacks are caused by Taliban infiltrators but the rest stem from personal animosities and cultural differences between Western troops and their Afghan allies.
Suspected US SEAL suicide
On Monday, ISAF also confirmed that a coalition soldier had been killed in eastern Afghanistan after an attack by Taliban fighters.
The attack was unrelated to the insider attack in Kabul, a statement said. NATO did not identify the service member or provide their nationality.
Earlier, the US defence department confirmed that the commander of an elite US Navy SEAL unit died in Afghanistan's Uruzgan province on Saturday.
A US military official said on Sunday that the death was being investigated as a suspected suicide, Reuters news agency and US media reported.