CNN) -- Syria announced Tuesday that it is expelling some diplomats from 11 countries, a week after those nations expelled Syrian officials in a coordinated response to a massacre and the government's violent crackdown on the opposition.
The move came as those countries looked for new ways to push for a halt in the violence, through the U.N. Security Council and other means.
Residents of Houla, the town that suffered the recent massacre, sent out a plea via Skype, saying they are without basic necessities.
"For more than 10 days now, the criminal regime forces have cut off basic food items from entering Houla area," said the statement from the opposition Houla Media Center.
"They stopped flour, gas and medicine from coming in, and they continue to cut off electricity because the main supplying plant was hit by the sporadic shelling. ... We call on relief and human rights organizations to help us and open humanitarian corridors for basic items so you do not become collaborators in the (regime's) massacres."
President Bashar al-Assad's regime denies responsibility for the massacre that left more than 100 people dead, nearly half of them children, and has said it is fighting to stop "armed terrorist groups."
At a meeting organized by the United Nations in Geneva, Syria agreed to new humanitarian measures, according to a statement from Kristalina Georgieva, European Union commissioner for humanitarian efforts.
"A comprehensive humanitarian response plan negotiated by the U.N. has finally been agreed by the government of Syria," she said.
"It is a positive but long-overdue step. Let me be me clear that I expect the Syrian government to fully cooperate and ensure the rapid implementation of the comprehensive humanitarian response plan. This is no more time to delay or reason to prevaricate. And once again, I want to remind all parties of their responsibility that they must respect and protect the lives of civilians as well as to respect the work of humanitarian personnel and to facilitate their access to people in need."
No details of the response plan were given.
To press for tough action against the Syrian regime, the United States is sending a delegation to Russia this week led by special adviser Fredrick Hoff, a senior Obama administration official said. The official was not authorized to speak on the record.
Russia and China have previously used their veto power to block U.N. resolutions that condemned al-Assad's regime.
Both countries have major trade deals with Syria.
Russian Deputy Foreign Minister Mikhail Bogdanov said talks between Russia and the United States "continue at various levels," according to the state-run news agency RIA Novosti.
Saudi Arabia's foreign minister, Prince Saud al-Faisal, spoke out against Russia on Tuesday after a meeting of the Gulf Cooperation Council.
"We feel that the position which Russia has taken so far at the Security Council is unjustified," he said. "And we hope that Russia will re-evaluate its stance towards this region, especially Syria. If Russia is careful about its relations with Syria, then I believe it is mistaken to stand as an obstacle against the popular Syrian position.
"It is time for Russia to change its position from standing by the Syrian regime to sincerely try to stop the violence and support a peaceful transition of power," al-Faisal added.
Syria's Foreign Ministry said diplomats from the United States, Britain, Switzerland, Turkey, France, Italy, Spain, Belgium, Bulgaria, Germany and Canada were being declared persona non grata.
Among them is U.S. Ambassador Robert Ford, who has been back in the United States since the U.S. government closed its embassy in Syria in February.
British Ambassador Simon Collis, who is also back in Britain, is on the list as well.
Turkey's ambassador and all members of the embassy -- diplomats and administrators -- are expelled, the Syrian Foreign Ministry said.
All members of the Canadian Embassy are listed as well.
Last week, Syria expelled the Dutch charge d'affaires after the Netherlands was among countries expelling Syrian diplomats.
Despite the expulsions, Syria "stresses the importance of dialogue based on principles of equality and mutual respect between nations, and diplomacy is the necessary vehicle to connect with countries to resolve conflicts between countries, and pending issues," the Syrian Foreign Ministry said in a statement. "We hope that those countries that took this step believe in adopting these principles to allow the relationship to go back to its normal state of being."
The opposition Local Coordination Committees of Syria reported that 44 people were killed Tuesday across several cities, including 12 in Latakia province, where clashes were under way between the opposition and regime forces on the outskirts of Hiffa.
Residents of the Hiffa area "have issued a call for help to the U.N. observers after the regime's shelling in the area, and are warning of an impending massacre with the entry of Shabiha to the city," the Local Coordination Committees said.
A U.N. official and the United States have blamed the Shabiha militia, acting on behalf of the government, for the recent massacre in Houla. Nearly half of the more than 100 victims were children.
The Syrian Observatory for Human Rights, another opposition group, also reported the clashes Tuesday on the outskirts of Hiffa, saying at least 11 opposition members were killed: two civilians and nine rebel fighters. Dozens of civilians were wounded, the group said.
Medical sources and activists report at least 22 members of the Syrian security forces and government militia killed as well, the observatory said.
Separately, "A colonel in the Syrian army was shot and killed outside his house, in the city of Deir Ezzor, by unknown gunmen," the observatory said on its Facebook page.
Syria, on state-run news agency SANA, said "armed terrorist groups" assassinated three officers: Lt. Col. Izz-Eddin Abdullah Sweidan, Col. Ahmad Abdul-Qader Haj Hattab and Brig. Gen. Anwar al-Saqqa.
Seventeen "army and law enforcement martyrs" were buried Tuesday, Syria said.
The head of the U.N. observer mission in Syria, Maj. Gen. Robert Mood, met with Syrian Deputy Foreign Minister Faisal Miqdad for more than an hour Tuesday in Damascus, the United Nations said.
Meanwhile, U.N. observers in Hama found the atmosphere tense, the United Nations said.
"There is heavy military presence and several roadblocks where residents are stopped and screened. Tanks and armored vehicles are still visible on the outskirts of the city. The streets are empty, and many shops are closed. Many residents have fled their homes, and those that remain are mourning the loved ones they have lost," a U.N. statement said.