Syrian authorities have blocked an aid convoy carrying emergency supplies from entering the Baba Amr district in the city of Homs, the International Committee of the Red Cross says.
The president of the Red Cross says the decision to deny aid groups access to Baba Amr is "unacceptable".
Jakob Kellenberger said the aid group would stay in Homs overnight in the hope of entering Baba Amr "in the very near future".
The Syrian government had given the Red Cross permission on Thursday to enter Baba Amr after security forces took the district from rebels. The convoy of seven aid trucks was carrying food, milk powder, medical supplies and blankets.
The announcement came as activists accused regime forces of carrying out execution-style killings and burning homes as part of a scorched-earth campaign. Syria has faced mounting international criticism over its bloody crackdown on the uprising. The UN has estimated that more than 7,500 people have been killed.
France said it is closing its embassy in Syria, a day after two French journalists escaped to Lebanon after being trapped in Homs. The United States and Britain have already closed their embassies in Syria.
Bassel Fouad, a Syrian activist who fled to Lebanon from Baba Amr, said a colleague there told him that Syrian troops and pro-government gunmen known as shabiha were conducting house-to-house raids. The UK-based Syrian Observatory for Human Rights also said it had received reports of 10 people killed.
In Geneva, a spokesman for the UN High Commissioner for Human Rights said the agency had received unconfirmed reports of "a particularly grisly set of summary executions" involving 17 people in Baba Amr after government forces entered.
The West has stepped up its criticism of Assad's regime amid mounting reports of atrocities. But Russia's Prime Minister Vladimir Putin blasted the West for backing the Syrian opposition against the government, saying it has fuelled the conflict.
Activist groups said protesters took to the streets in towns across Syria, many of them met with tear gas, gunfire and arrest campaigns by Syrian security forces. The Observatory said 10 people were killed in the town of Rastan near Homs when a mortar landed near marchers. The LCC said 13 were killed the same event, among 37 reported dead nationwide.
www.icrc.org/(International Committee of the Red Cross)