BEIRUT (AP) -- Syria blocked a Red Cross convoy Friday from delivering badly needed food, medical supplies and blankets to a rebellious neighborhood of Homs cut off by a monthlong siege, and activists accused regime troops who overran the shattered district of execution-style killings and a scorched-earth campaign.
Humanitarian conditions in the former rebel stronghold of Baba Amr have been described as catastrophic, with extended power outages, shortages of food and water, and no medical care for the sick and wounded.
British Prime Minister David Cameron called Homs "a scene of medieval barbarity."
Syrian state TV showed burned-out and destroyed buildings in Baba Amr, a western neighborhood of Homs, which was covered with a blanket of fresh snow.
Syrian government forces took control of Baba Amr on Thursday after rebels fled the district under constant bombardment that activists said killed hundreds of people since early February. The Syrian regime has said it was fighting "armed gangs" in Baba Amr, and had vowed to "cleanse" the neighborhood.
"It is unacceptable that people who have been in need of emergency assistance for weeks have still not received any help," said Jakob Kellenberger, president of the International Committee of the Red Cross.
The Red Cross said it had received permission from the government of President Bashar Assad on Thursday to enter Baba Amr, on the western side of Homs, and a convoy of seven trucks carrying 15 tons of humanitarian aid was poised to do so, but authorities then blocked their access. There was no explanation from the government about the change.
"We are staying in Homs tonight in the hope of entering Baba Amr in the very near future," Kellenberger said.
Bassel Fouad, a Syrian activist who fled to Lebanon from Baba Amr, said a colleague there told him Friday that Syrian troops and pro-government gunmen known as shabiha were conducting house-to-house raids.
"The situation is worse than terrible inside Baba Amr," Fouad said. "Shabiha are entering homes and setting them on fire."
His colleague said the gunmen lined 10 men up early Friday and shot them to death in front of a government cooperative that sells subsidized food. Syrian forces were detaining anyone over the age of 14 in the three-story building, he added.
"They begin at the start of a street and enter and search house after house," he said. "Then they start with another street."
The Britain-based Syrian Observatory for Human Rights also said it had received reports of 10 people slain in front of a co-op and called on the Red Cross team heading to Homs to investigate claims by residents the building is being used a prison. Another group, the Local Coordination Committees, said 14 were killed.
The claims could not be independently verified. Rupert Colville, a spokesman for the U.N. High Commissioner for Human Rights, said in Geneva that the agency had received unconfirmed reports of "a particularly grisly set of summary executions" involving 17 people in Baba Amr after government forces entered.
Colville said his office was seeking to confirm the reports and called on both government and rebel forces to refrain from all forms of revenge attacks.
Syria has a fragile mix of ethnic groups including Sunnis, Shiites, Christians and the minority Alawite sect, to which Assad and the ruling elite belong. Homs, the country's third-largest city, has emerged as a key battleground and has seen an alarming rise in sectarian tensions and reprisal killings.
The European Union committed itself to document war crimes in Syria to set the stage for a "day of reckoning" for the country's leadership, in the way that former Yugoslav leaders were tried for war crimes in the 1990s by a special U.N. tribunal.
EU leaders in Brussels condemned Assad's regime for its nearly yearlong crackdown on an uprising that began with mostly peaceful protests but has veered toward civil war, with Syrian forces firing heavy artillery against civilians. The U.N. has estimated that more than 7,500 people have been killed, while activists put the death toll at over 8,000.
"We will make sure -- as we did in Serbia -- that there is a day of reckoning for those who are responsible," said Cameron, who accused the Assad regime of "butchering its own people."
"It is very important that we set out the war crimes that effectively are being committed, that we write them down, we take the photographic evidence, we bring it together and ... make sure that the day of reckoning will come," he told reporters.
The EU leaders pledged to step up sanctions against the Damascus regime "as long as the violence and human rights abuses continue." They again called on Assad to resign.
French President Nicolas Sarkozy said his country is closing its embassy in Syria, a day after two French journalists -- one of them wounded -- escaped to Lebanon after being trapped for days in Baba Amr for nine days. Britain and the United States have already closed their embassies.
Russia, a staunch ally of Syria, blasted the West for backing the opposition, with Prime Minister Vladimir Putin calling for both the rebels and the government forces to pull out of besieged cities to end the bloodshed.
"Do they want Assad to pull out his forces so the opposition moves right in?" Putin said at a meeting with Western newspaper editors in remarks on state TV. "Is it a balanced approach?"
Sarkozy greeted Edith Bouvier, a journalist for Le Figaro, and William Daniels, a photographer, after they flew to a military airport in Villacoublay, France, from Beirut.
Bouvier was taken off the plane on a stretcher. She sustained several fractures to a leg during a rocket attack on Feb. 22 that killed two Western journalists -- American-born reporter Marie Colvin and French photographer Remi Ochlik -- and wounded a British photographer, Paul Conroy.
Conroy and Spanish reporter Javier Espinosa also were smuggled out of Syria.
Red Cross spokesman Bijan Farnoudi told The Associated Press that the organization has the bodies of Colvin and Ochlik and was taking them to Damascus. Activist videos posted online Thursday purported to show the burials of Colvin and Ochlik in Baba Amr this week. The Syrian government news agency said the bodies were exhumed after Baba Amr fell so they could be repatriated. But in an obviously erroneous report, it said Espinosa's body was among them, even though he appeared on international TV shows Friday, detailing his escape.
Activists said protesters took to the streets in towns elsewhere across Syria Friday, with security forces unleashing tear gas and gunfire, and making mass arrests.
The Observatory said 10 people were killed in the town of Rastan near Homs when a mortar shell landed near marchers. The LCC said 16 were killed in the same event, among 65 reported dead nationwide.
Amateur videos posted online by activists a protest in Rastan of about 200 youths singing and flashing the "V'' sign for victory until a gunshot sent them fleeing. The videos showed gruesome images, including a bloodied corpse slumped in front of a shop and a severed head in a pool of blood.
Associated Press writers Frank Jordans in Geneva, Elaine Ganley in Paris, Albert Aji in Damascus, Vladimir Isachenkov in Moscow and Robert Wielaard in Brussels contributed reporting.