Opposition networks said between 28 and 38 people were killed, one day after protesters massed in the city to greet the U.N. peace monitors, The Wall Street Journal reported.
Mousab al-Hamadee, a resident of Hama who is active in the opposition to the regime of President Bashar Assad, told the newspaper the regime "decided to punish the people of Hama because they were brave enough to come out to meet the monitors."
"The regime wanted to send a message to other cities," al-Hamadee said.
U.N. observers were sent to Syria to help protect Assad regime opponent. Monday's violence was said to be perhaps the worst in Syria since a cease-fire was supposed to have gone into effect April 12, the Journal said.
White House press secretary Jay Carney said Monday the Obama administration supports the U.N. monitoring mission, "but we understand the sobering challenge it represents in the atmosphere that has been created by the Assad regime." He said the United States will work with its "partners and allies to continue to pressure and isolate the Assad regime, to make clear to everyone internationally that siding with the Assad regime is a folly because Assad will go down as a brutal dictator who brutally murdered his own people -- not the kind of friend you really want in the world."
"And we will continue to work with the United Nations and with the 'Friends of Syria,' and all other partners in providing assistance to the Syrian people, to helping the opposition function and organize itself and function more efficiently, and isolating and pressuring the Assad regime."
Notable deaths of 2014 [PHOTOS]