Aides to Amos, who was accompanied by officials of the Syrian Red Crescent, said she would not make any statements during her three-day visit, The New York Times reported.
A Red Cross-Red Crescent employee, speaking on condition of anonymity, said when the government granted permission for the aid group to enter the Homs neighborhood of Baba Amr, "suddenly, Valerie Amos changed all her plans for the day and accompanied the team to find out that most of the Baba Amr population had left when the fighting was raging in Baba Amr."
The Assad regime had refused for a month to let Amos visit.
Before traveling, Amos said she intended "to urge all sides to allow unhindered access for humanitarian relief workers so they can evacuate the wounded and deliver essential supplies."
Amos said she planned to leave the Syrian capital Friday.
Her visit was to be followed Saturday by that of Kofi Annan, a former U.N. secretary-general appointed last week as a special representative to Syria for the United Nations and the Arab League.
Annan said he intended "to seek an urgent end to all violence and human-rights violations, and to initiate the effort to promote a peaceful solution to the Syrian crisis."
Syria "welcomes" Annan's visit, the state-run Syrian Arab News Agency reported Monday.
Syria repeatedly has barred aid workers from the devastated part of Homs.
President Bashar Assad said he was determined to press on in his bid to crush protesters, who he described as terrorist gangs financed by hostile foreign powers.
"The Syrian people, who have in the past managed to crush foreign plots ... have again proven their ability to defend the nation and to build a new Syria through their determination to pursue reforms while confronting foreign-backed terrorism," SANA quoted him as saying.
State television showed what it said were residents returning on foot to the Baba Amr neighborhood, held by rebels until they were defeated Thursday by Syria's elite 4th Armored Division, led by Brig. Gen. Maher Assad, a younger brother of the president, after a monthlong siege.
TV images showed men, women and children slogging past ruined and bullet-pocked buildings.
Other images showed a cramped tunnel state television said was used to smuggle arms to rebels.
But locals told British newspaper The Guardian the reports were fabricated.
"No one has tried to go back there," one Homs resident in a neighborhood next to Baba Amr told the newspaper.
"It makes me laugh when I see state TV. We know that it is untrue."
Troops loyal to the regime told the aid workers the neighborhood was sealed, citing security problems.
Violence continued across Syria, with armored vehicles and tanks massed on the western fringe of the city of Herak, in Daraa province, attacks intensifying in Rastan, 12 miles north of Homs, and raids mounting in the city of Deir al-Zor, in northeastern Syria, opposition organizations said.
The reports could not be independently verified.
U.S. President Barack Obama Tuesday called the Syrian bloodshed "heartbreaking and outrageous."
But Obama told a news conference he was not prepared to send U.S. forces to try to stop the carnage or to help overthrow Assad, as some Republicans in Congress have urged.
He added Assad has "lost legitimacy" and his downfall is a question of "when, not if."