Kabul - Afghan President Hamid Karzai expressed grief on Tuesday over the Boston marathon bombings, which killed three people and injured more than 100 in the US city.
Karzai in a statement denounced what he described as terrorist attacks in the "strongest possible terms".
"Having suffered from terrorist attacks and civilian casualties for years, our people feel better the pain and suffering arising from such incidents," he said.
The Afghan leader, who at times has tense relations with Washington but whose US-backed government has been fighting a Taliban insurgency since 2001, offered condolences and sympathies to families of the victims and the American people.
Suicide and other bombings are the main cause of civilian casualties in Afghanistan, where about 2 800 civilians died last year.
Security was stepped up in major cities across the United States following Monday's blasts which evoked memories of the 11 September 2001 attacks.