Americans living in Pakistan were warned today to avoid popular markets and restaurants, as the threat of violence there remains very high.

The U.S. embassy in Islamabad has stepped up its warning to American citizens, saying it has received "non-specific information regarding terrorist attacks, possibly suicide attacks" against U.S. interests and places frequented by Westerners.

Last year, a suicide attack in Karachi killed an American working at the U.S. consulate, along with his driver. 

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Such attacks had been rare in Pakistan, but since the beginning of the year, six incidents have been reported, hitting both military and civilian targets. Officials fear the increase is being fueled by the ongoing U.S. occupation of Iraq.

The State Department warning expands on earlier messages, suggesting attacks could take place in Islamabad, Karachi, Lahore and Peshawar. Pakistani officials have also warned of fresh attacks and have boosted security in major cities.