The shells hit Yarmouk camp on the southern outskirts of Damascus on Thursday.
Yarmouk camp and the districts surrounding it have borne the brunt of fighting in Damascus over the past few months.
Residents of the camp say that Yarmouk has been closed off from neighboring districts and that they hear regular clashes.
At least 20 people died in September when mortar shells slammed into the Palestinian refugee camp.
Syria has been experiencing unrest since March 2011. Many people, including large numbers of security forces, have been killed in the turmoil.
The Syrian government says the chaos is being orchestrated from outside the country, and there are reports that a very large number of the militants are foreign nationals.