At least 10 local militiamen and seven civilians were killed by the Taliban in southern Afghanistan on Wednesday, an official said.
"Ten Afghan policemen and seven civilians were poisoned and then shot at a (police) outpost early Wednesday in Andar district," Musa Akbarzada, the provincial governor for Ghazni, said.
He could not confirm who poisoned them, but said he believed it was one of their own comrades.
"The (seven) civilians were the guests of one of the policemen," the governor told dpa.
He said the authorities had detained one policeman for questioning to find out if he was involved in the incident.
The Taliban claimed responsibility for the attack, saying 19 policemen were killed and their weapons and vehicles were taken by their fighters.
"The Arbakis in that checkpoint were teasing people, robbing their properties, in Andar district. So, the mujahedeen (freedom fighters) attacked the post, killing 19," Zabihullah Mujahid, the militants' spokesman said.
He claimed there were no civilians in the checkpoint.
He called the attack "an obligation to save people" from the Arbakis, a term he used to refer to the Afghan Local Police, the government-supported militia financed by the US to protect remote areas where Afghan soldiers and national police are not available.
In recent months, there has been an increase in violence in the Andar district as civilians, backed by local strongmen, have taken up arms against the Taliban.
The militias have often been criticized for alleged reports of human rights violations and abuses.
The Andar attack was the latest in a series of attacks in which Taliban infiltrators have killed security forces.
In December and January, at least 20 policemen were killed in similar fashion in various parts of the country.
In Kabul, six Afghan army personnel and one civilian were injured on Wednesday when a Taliban suicide bomber targeted a military bus in Kabul.