BAGHDAD, Iraq — Ten American troops were killed yesterday in four separate incidents in Iraq, and a mortar attack that killed at least eight people and wounded dozens in a second-hand goods market was followed closely by a suicide bombing in Baghdad’s mainly Shiite district of Sadr City, authorities said.

“Our thoughts and prayers go out to those family members who have lost loved ones today,” American military spokesman Lieutenant Colonel Christopher Garver said. The military confirmed that the 10 Americans had died but gave no further details.

The two mortar rounds landed and exploded in the Haraj Market in a mixed Shiite-Sunni area in northern Baghdad, police officers Ali Mutab and Mohammed Khayoun, who provided the casualty totals, said.

About 25 minutes later, a suicide bomber on a bus in Sadr City detonated explosives hidden in his clothing, killing two people and wounding 15, police First Lieutenant Thaer Mahmoud said.

It appeared to be the first attack by suspected Sunni Arab insurgents on the large slum since November 23, when a bombing and mortar attack killed 215 people in the deadliest single attack since the Iraq war began more than three years ago.