Militants launched an attack, on Friday, on the U.S. consulate in the western Afghan city of Herat, about 80 miles from the Dogharoun border between Iran and Afghanistan, killing at least three people, news reports said, citing Afghan security officials.

The attack in Herat, western Afghanistan’s main city, which has a strong Taliban presence, adds to worries that the region could face a security breakdown after U.S. troops pull out of the country in 2014, after 12 years of war against insurgents.

The U.S. embassy in Afghanistan’s capital, Kabul, said all U.S. nationals in the consulate in Herat were safe, Reuters reported. An embassy spokesman described the attack on the consulate as “complex” and said that it included a car bomb.

Abdul Raoof Ahmadi, a spokesperson for a local hospital, said two policemen and a security guard were killed and 17 others were injured in the attack, Reuters reported.

Herat police chief Gen. Rahmatullah Safi told Reuters that militants were fighting outside the consulate while Afghans and Americans were trapped inside.

The Taliban claimed responsibility for the attack, saying their aim was to show “the Americans that they are not safe anywhere in this country,” according to a Taliban statement reported by Reuters.

Meanwhile, al Qaeda chief Ayman al-Zawahiri, in a speech marking the twelfth anniversary of the attacks in the U.S. on Sept.11, 2001, called for measures to keep "America in tension.”

“We should bleed America economically by provoking it to continue in its massive expenditure on its security, for the weak point of America is its economy, which has already begun to stagger due to the military and security expenditure,” Zawahiri said, according to SITE intelligence group, which translated his 72-minute address, posted on jihadist forums.

“And keeping America in tension and anticipation only costs a few disparate attacks here and there, meaning as we defeated it in the gang warfare in Somalia, Yemen, Iraq and Afghanistan, so we should follow it with that war on its own land,” he said, and urged Islamists fighting in conflict-ridden Syria not to cooperate with non-Islamists.