Nearly 5,000 people have been killed in a brutal crackdown by forces loyal to Syrian President Bashar Assad on pro-democracy protests, a leaked United Nations report said on Monday, as Syrian activists said they a feared large-scale attack on the flashpoint city of Homs.

According to the French news agency AFP, UN rights chief Navi Pillay is to cite this figure when she addresses the Security Council, while also expected to report that more than 14,000 people are estimated to have been detained and 12,400 have fled into neighboring countries.

Moreover, the AFP report claimed that the UN will report that more than 200 people were killed from the beginning of this month.

Commenting on the report following a meeting with Pillay, German Foreign
Minister Guido Westerwelle said: "I am really shocked about what I heard about the atrocities in Syria. Five thousand people were killed, civilians, people who ask for their freedom and civil and human rights."

Updated UN data on the Syria crackdown came as CNN quoted Syrian activists who had feared that Assad's security forces were about to end a full-on military siege on the flashpoint city of Homs, and were about to engage in a disastrous attack.

"People are very afraid," Wissam Tarif, a human rights activist in Beirut, Lebanon, told CNN with the organization Avaaz, who is in touch with people in Syria.

Tarif said that was informed that there were enough troops around Homs "to take over the city," telling CNN that casualties have been increasing "in very big numbers" over the past couple of days.

"People are afraid that the army might now invade the city," the activist added.

According to Lt. Col. Mohamed Hamdo of the opposition's Free Syrian Army, Syrian forces gave the city's residents a 72-hour warning, adding that the military has dug trenches around Homs and largely cut it off.

Opposition figures have warned that the President Bashar al-Assad's regime might commit a similar massacre to the 1982 attack on the province of Hama under leadership of late president Hafez al-Assad, father of Bashar.

The Hama massacre was then supervised then by Hafez al-Assad's younger brother, Rifaat al-Assad, effectively ending the campaign which begun in 1976 by Sunni Islamic groups, including the Muslim Brotherhood, against al-Assad's regime.

Reports at the time stated that between 10,000 and 28,000 people were killed by government forces.