ISLAMABAD (REUTERS) - Men claiming to be Islamic militants shot and wounded an American woman in the southern Pakistani city of Karachi on Thursday, leaving leaflets in her car naming her and saying they had targeted her because she was American, police said.

Gunmen on motorbikes shot Debra Lobo in the face and the hand as she drove home from the dental college where she worked as a vice-principal.

Police said it was unclear if the attack had actually been carried out by militants, or by men posing as militants.

Pakistan is plagued by an Islamist Taleban insurgency but is also home to many other militant groups and criminal gangs.

Some Taleban splinter groups have pledged allegiance to Islamic State in Iraq and Syria, or ISIS.

Extortionists and other criminals also often claim to be militants.

"Pamphlets claiming the attack have been found in the car, giving impression that some banned (militant) outfit carried out the attack," deputy police superintendent Nasir Lodhi told Reuters.

The English version of the pamphlet read: "Oh crusaders, we are the lions of Dualat al Islamia, the falcons of the caliph. Today we killed this Kansas lady Lobo, we shall lie and wait and ambush you and kill you wherever you may be and confined and besiege you in America and then god willing... we will burn American."

An Urdu version of the pamphlet was also left.

None of the references pointed to any known Islamist militant group.

The leaflet said the attack was revenge for the killing of five suspected militants in Karachi the day before.

Lodhi said Lobo was in her mid-50s, had been living in Pakistan since 1998, and was married to a Pakistani.

Americans have been targeted in Pakistan before.

The US contractor Warren Weinstein was kidnapped from the eastern city of Lahore in 2011. Al-Qaeda's media wing has released videos of him but he remains in captivity.