Syrian troops and their Hezbollah allies trying to capture the strategic border town of Qusair engaged in fierce fighting with rebels Saturday.
An activist group, the Syrian Observatory for Human Rights, said clashes took place inside Qusair and in villages around it.
The fighting came as U.N. Secretary-General Ban Ki-moon warned that all parties will be held accountable for atrocities committed against civilians in Qusair.
Syrian troops and Hezbollah fighters have come closer to capturing Qusair, where fighting has been raging in recent days. The town is important for supply routes used by forces backing the government of Syrian President Bashar al-Assad and the opposition.
In other news, the Syrian conflict again spilled across the border into Lebanon, where rockets landed in an eastern region on Friday. Security officials say at least six rockets fired from Syria hit the eastern Bekaa region of Lebanon but did not cause casualties.
Bekaa is a stronghold of Hezbollah, a Lebanese militant group.
Lebanon, which has not officially taken a side in the Syrian civil war, has been hit in recent months by a number of rockets, many of which have struck pro-Hezbollah regions.
Clashes in Lebanon between supporters and opponents of Mr. Assad have killed dozens of people in recent weeks.