CHITRAL, Dec 28: Police said here on Tuesday they had detained four suspects, two of them belonging to a banned militant organization, for questioning in a case of double murder and arson attack on the Aga Khan Health Services.

"We have detained four people for questioning," a police official in the snow-bound northern district told Dawn by telephone. "We are looking into different aspects and investigating the case from different angles", the official said.

He said that a brother of one of the two workers of the AKHS shot and killed by unidentified gunmen had lodged a report with the police alleging his brother had been killed because of a land dispute and named their rivals for having committed the crime.

The police official said that they had detained two people from the rival side, while two others belonging to a banned militant outfit had also been picked up for questioning to see if they had any role in the murder and arson attack on the AKHS offices.

Unidentified gunmen shot and killed a security guard and a driver of the AKHS and set fire to five vehicles parked in the compound on Sunday night. The police said that they had recovered empty cartridges of AK-47 assault rifle and a 30 bore pistol.

"We don't know yet whether the attack was carried out by militants opposed to the AKHS or it was purely the result of a land dispute involving the security guard and in which the driver was killed just because he happened to be there", the official said.