SANAA (Reuters) – Yemen has boosted security at energy installations to guard against militant attacks, a government official said on Sunday, as Sanaa escalated its war against al Qaeda. “The security measures have been strengthened for some time. But we took additional measures around oil institutions and the gas project in Shabwa,” the official told Reuters, speaking on customary condition of anonymity.

He said the measures were put in place “in case of any terrorist attacks.” Other security officials said the heightened security had been put in place on Saturday, a day after an air strike in northern Yemen killed six al Qaeda militants.

Yemen, which gained a reputation as a haven for al Qaeda after the September 11, 2001 attacks in the United States, came under the spotlight after crackdowns on the group in Pakistan and Afghanistan raised concern it was becoming a training and recruiting center for militants.

The Yemen wing of the global militant network, Al Qaeda in the Arabian Peninsula, has strongholds in Yemen’s eastern province of Hadramaut and the towns of Maarib and Shabwa, where oil and gas fields of major international companies are located.

Yemen is an oil producing minnow in a region of export giants such as neighbor and top exporter Saudi Arabia, so interruption of its 300,000 barrels per day (bpd) of oil output would have little impact on international energy markets.

But Yemen relies on oil revenues for 70-75 percent of public revenue and more than 90 percent of export earnings. Any interruption to that income would put pressure on the budget of an already desperately poor country that says it needs billions of dollars of economic aid.

Yemen declared open war on al Qaeda on Thursday and warned citizens against aiding the global militant group. Troops were sent last week to join a drive against al Qaeda in three provinces.

On Friday, an air strike killed six al Qaeda militants in northern Yemen in an attack one analyst has said would be a significant blow to al Qaeda’s Yemen-based wing.

The local headquarters of several large Western oil companies are clustered in the capital and the residential area housing Western oil workers in Sanaa has been attacked before.