UNICEF spokeswoman Marixie Mercado told reporters that the agency has received "reliable and consistent reports of children being among the people targeted by snipers in Misrata."
She said she couldn't say how many children were killed or injured by Moammar Gadhafi's forces.
The international committee of the Red Cross sent a team on Friday to investigate the claim.
Militiamen and pro-government forces are battling for control of a key road in Misrata that links to a port that serves as a critical lifeline for besieged civilians and opposition fighters.
Heavy shelling was heard at nightfall outside the city, where some neighborhoods have been nearly abandoned after residents fled to safer areas during weeks of fighting. Nearly all buildings were pockmarked from gunfire.
Misrata, the country's third largest city, is the only significant rebel outpost in Gadhafi-ruled western Libya.
But NATO has been cautious about waging bombing runs in Misrata because the fighting in mostly within civilian areas. Growing indications of a drawn-out conflict in an OPEC nation pushed oil prices to levels not seen in more than two years ago. The Associated Press contributed to this report.