Thousands of Syrian refugees have been fleeing into Turkey, officials there say, as UN chief Ban Ki-moon warns the crisis is escalating.
More than 2,300 fled on Wednesday, by far the highest number in one day.
Earlier, the UN called for the Syrian government to "urgently" implement an agreed ceasefire.
The approach of the deadline for a ceasefire seems to have brought an intensification rather than reduction in violence.
In the Jouret al-Shiyah quarter of Homs, shells or rockets were falling at a rate of four in 30 seconds.
Activists accuse the government of trying to complete its crackdown come what may; government officials say it is the rebel fighters who are exploiting the impending withdrawal of the military from towns and cities to improve their position.
Activist groups say at least 60 people were killed in shelling or shooting by security forces on Thursday in various parts of the country, mainly the central city of Homs and Idlib province in the north-west.
Syrian President Bashar al-Assad, who is fighting to crush a year-long uprising, agreed late last month to a UN-Arab League peace plan which sets a 10 April deadline for a ceasefire.
