Syria Army Advances in Aleppo after U.S. Drops Russia Talks

Syrian regime forces advanced against rebels during intense street battles in the heart of Aleppo on Tuesday, after the United States abandoned talks with Russia aimed at reviving a ceasefire deal.

Washington said its decision did not mean it was "abandoning the pursuit of peace", as Moscow called for "political wisdom" while announcing the deployment of its S-300 missile system to the port of Tartus.

And the U.N. rights chief called for action to halt the "ghastly avalanche of violence" unfolding in Syria's second city, which is reeling from some of the most brutal fighting in the five-year conflict.

The Syrian army announced a major Russian-backed military push nearly two weeks ago to capture the rebel-held eastern half of Aleppo, once the country's commercial hub.

On Tuesday, loyalists seized high-rise buildings from rebels in the city center, pushing north towards other opposition districts.

The Syrian Observatory for Human Rights said regime forces were "gradually advancing" after street battles on the front line dividing the rebel-held east from the government-controlled west.

"They are focusing on the tall buildings, which were once government administration buildings, because they can monitor entire streets and neighborhoods from there," said Observatory head Rami Abdel Rahman.

State news agency SANA reported rebel shelling on the government-held west, including on the Aleppo University campus, killed six people. 

- 'Patience run out' -

More than 300,000 people have been killed since the conflict erupted in March 2011, and the latest attempt at securing a diplomatic solution to the war has fallen apart.

Washington announced late Monday that it would suspend joint efforts to reinstate a nationwide truce, accusing Moscow of abetting strongman Bashar Assad's assault on Aleppo.

"Everybody's patience with Russia has run out," White House spokesman Josh Earnest told reporters.

A U.S. official said U.S. Secretary of State John Kerry is "laser-focused" on finding a diplomatic solution, but his talks with Russian counterpart Sergei Lavrov on the crisis were over.

Kerry said Tuesday the decision was one "we did not come to lightly."

"We are not abandoning the pursuit of peace, we are not going to leave the multilateral field, we are going to continue to try to find a way forward in order to end this war," he added, offering fierce criticism of Moscow.

"People who are serious about making peace behave differently from the way Russia has chosen to behave," he said.

The Kremlin meanwhile said it "would like to hope for the presence of political wisdom and the continuation of exchanges on particularly sensitive issues that are necessary for maintaining peace and security."

And Lavrov said Moscow was "not shirking our responsibility but consider that the crisis can only be resolved collectively."

Russia's defense ministry said later it had sent an S-300 missile system to its naval facility in the Syrian city of Tartus, a measure it says is meant to bolster its security.

The U.S.-Russia truce plan for Syria had envisioned an end to hostilities, increased aid deliveries to besieged populations, and eventual coordination between rivals Moscow and Washington against jihadists.

But the truce collapsed after a week, with Russia blaming Washington for failing to convince rebels to distance themselves from jihadist fighters.

Russia and the U.S. will keep a communications channel open solely to ensure their separate anti-jihadist bombing campaigns do not get in each other's way.

- U.N. call for action -

U.N. rights chief Zeid Ra'ad Al Hussein decried the "ghastly avalanche of violence and destruction" in east Aleppo, saying 100 children had been killed there in the past 10 days.

He urged the Security Council to introduce a limit on its members' veto power, to prevent countries like Russia blocking the referral of Syria's conflict to the International Criminal Court in The Hague.

On Monday, the largest hospital in the rebel-held side of Aleppo was completely destroyed in an aerial attack, according to the Syrian American Medical Society, which supports the facility. 

Only five hospitals remain operational for the estimated 250,000 people living under a crippling government siege in east Aleppo.

Arab League chief Ahmed Abul Gheit told an emergency meeting that the situation in Aleppo was "carnage," calling for an "urgent ceasefire."

In northeast Syria, the toll in a suicide attack at a wedding rose to 34 people, the region's Kurdish government said.

The Islamic State group claimed the attack, saying one of its members had fired on a gathering near Hasakeh city before blowing himself up, though it did not mention a wedding.

The bombing left rows of seats covered in blood at the wedding hall in Hasakeh province.

"I was taking pictures of the party, and all of a sudden I felt a huge explosion," said wedding photographer Walid Mohammad.

"I saw so many people die -- small kids, old people."