KARACHI, Pakistan

At least nine suspected militants were killed during an ongoing security operation in northwest Pakistan, police said on Tuesday.

The suspected militants were killed in the Upper Dir district of northwestern Khyber Pakhtunkhwa province, near the Afghanistan border, over the past three days, a city police chief, Bilal Haider, told reporters.

A large-scale military operation is also underway in the neighboring Bajaur tribal district, where authorities say militants loyal to the outlawed network Tehreek-Taliban Pakistan are hiding.

The South Asian country has been reeling from mounting terrorist attacks over the past few years, for which it accuses "Afghanistan-based" militants.

Kabul, however, denies the accusation.

Meanwhile, at least three miners were killed due to the release of poisonous gas in a coal mine in the Bolan district of southwestern Balochistan province, rescue officials said.

Pakistan has a history of deadly mine accidents, many of them the result of poor safety standards.