Declan Walsh reports: An attack early Thursday on a major Pakistani air force base where some of the country’s nuclear weapons are thought to be stored set off a heavy gun battle in which eight attackers and one security official were killed.

The authorities believe Islamic militants are responsible for the attack, on the Minhas air force base in Kamra, 25 miles northwest of the capital, Islamabad. The assault was a stark reminder of the militants’ determination to attack Pakistan’s most sensitive installations despite continuing military operations in their tribal hide-outs.

The sprawling air base, in the Attock district of Punjab, is believed by some Western experts to be one of the locations where elements of Pakistan’s nuclear stockpile, estimated to include at least 100 warheads, is stored. But Pakistani officials have denied that.

Over the past several years there have been several attacks on bases that are believed to be involved in the country’s nuclear program, but most evidence has suggested that the militants were targeting the country’s military capability in general.