Pope Francis has said he is "deeply grieved" by news of the loss of life and grave injuries caused by two bomb explosions at the Boston Marathon.

Three people were killed, including an eight-year-old boy named as Martin Richard who is reported to have been waiting for his father to finish the race.

More than 150 people were injured in the bomb blasts, which happened close to the finishing line at around 14:50 local time (18:50 GMT) on Monday.

In a telegram to the Archbishop of Boston, Cardinal Sean O'Malley, the Pope gave assurances of his "sympathy and closeness in prayer" to the victims.

Quoting Romans 12.21, the Pope urged the people of Boston to be "united in a resolve not to be overcome by evil, but to combat evil with good, working together to build an ever more just, free and secure society for generations yet to come".

The Salvation Army USA said in an update that it had stationed three canteens in the immediate aftermath of the bombings to support emergency personnel, people evacuated from buildings, and others affected by events.

Salvation Army officers were also on hand in area hospitals to provide pastoral care to the injured.

"We thank God for the meaningful conversations that occurred during this difficult time," said Major Dave Kelly, Divisional Commander of The Salvation Army's Massachusettes Division.

"I am deeply grateful for the quick response, compassionate spirits, and heart for ministry with which our officers, staff, and volunteers responded."