Syria mounts feared all-out ground assault DAMASCUS, Syria, March 1 (UPI) -- Syrian troops mounted a feared all-out ground assault on a rebel-held Homs neighborhood Thursday as Damascus denied a top U.N. envoy entry into the country. The Baba Amr neighborhood, a stronghold of opposition to President Bashar Assad, lost all power and communications links Wednesday, including satellite phones activists have used to transmit news and images of the fighting to the outside world, so it was difficult to confirm what was happening. At least 16 people were killed in Homs Wednesday out of 29 nationwide, the Local Coordinating Committees said before communications were cut. Other opposition groups said for the first time they could not provide casualty figures for Homs because they were unable to reach their contacts. But tens of thousands of civilians were reported cowering in ruined buildings, shelters and basements devastated in a daily government onslaught that began nearly a month ago, the British newspaper The Daily Telegraph reported. The fighting pitched the opposition Free Syrian Army, made up of defected Syrian army personnel, against Assad brother Brig. Gen. Maher Assad, commander of the feared 4th Armored Division, the Syrian armed forces' most elite, best-trained and best-equipped unit. The division pounded the area from four sides with mortar and rocket fire Wednesday, activists said before communications were cut. A statement attributed to the Free Syrian Army and posted on a Facebook page run by a Baba Amr activist now outside the country, said rebel soldiers kept the division from entering the neighborhood Wednesday. The official Syrian Arab News Agency did not mention Homs other than to say a nurse died when an "armed terrorist group" opened fire in a government-run Homs hospital. It also said customs agents had seized small caches of light weapons being smuggled into the country from Turkey. Snow and rain fell in Homs Thursday morning. The Syrian army distributed gas masks to its soldiers last month, the British newspaper The Daily Telegraph reported, while Assad forces transferred grenades and mortars containing chemical agents to a Homs school building, the Israeli newspaper Haaretz reported. Opposition figures expressed concern the moves could signal the regime's intention to unleash a fierce street attack on Homs residents and use chemical weapons against its citizens. In Washington, the State Department said it summoned Syria's top diplomat, Charge d'Affaires Zuheir Jabbour, to "express our outrage over the month-long campaign of brutality and indiscriminate shelling" of Homs. The Syrian Embassy in Washington had no immediate comment. Syria stymied U.N. efforts to address the crisis by refusing Wednesday to let the top U.N. humanitarian official, Valerie Amos, to enter the country. U.S. Ambassador to the United Nations Susan Rice called the visa denial shameful and the Assad regime's disregard for its people callous and reprehensible. The visa denial came despite lobbying from Syrian ally Russia to allow it. Moscow also endorsed attempts to bolster medical and other aid to the country. Amos said she was "deeply disappointed" by the rejection, and she supported a call by the International Committee of the Red Cross to help meet the medical and other humanitarian needs of civilians. The United Nations and Arab League last week appointed former U.N. Secretary-General Kofi Annan as their joint special envoy to Syria. Annan told reporters at the United Nations Wednesday he hoped to "plead" with Bashar Assad to work with the international community to peacefully resolve the nearly year-old conflict. Damascus sad it needed more information about his mission's goals before it would consider letting him in. U.N. Secretary-General Ban Ki-moon said a letter to Assad explaining Annan's mission "was on its way." Annan told reporters, "The message is clear -- the killing and violence must stop."