According to the BBC, dozens of tankers were being filled with fuel for NATO troops in Afghanistan when the attack took place on Monday morning.
"Between 10 to 12 men armed with automatic weapons stormed the depot from two sides. They opened indiscriminate fire on the tankers," said Umar Farooq, a senior Islamabad police official.
This is the latest in a series of attacks on convoys travelling by land through Pakistan to supply NATO forces in Afghanistan.
Last Friday, dozens of trucks carrying supplies for the troops were set on fire in Sindh.
The Tehrik-e-Taliban Pakistan had claimed responsibility for the attack.
It came amid a row between NATO and Pakistan after a recent cross-border air strike by International Security Assistance Force killed three Pakistani troops.
In response to the heightened tension, Pakistan has closed down a key supply route for forces.
In a meeting with Central Intelligence Agency Director Leon Panetta, Pakistan President Asif Ali Zardari and Prime Minister Yousaf Raza Gilani had also conveyed to the United States that any violation of its sovereignty was unacceptable to Pakistan.
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