Britain said Friday it agreed with the United States' assessment that the Syrian regime has used chemical weapons and called for a "strong, determined" international response.

Foreign Secretary William Hague said Britain would be discussing that response "urgently" with the United States, France and other countries, including at a G8 summit next week.

Syrian troops and rebels fought the heaviest battles in months Friday Aleppo, Syria's largest city, a day after U.S. officials said Washington has authorized sending weapons to opposition fighters for the first time.

The Britain-based Syrian Observatory for Human Rights said the clashes concentrated in the eastern rebel-held neighborhood of Sakhour, calling the fighting "the most violent in months." It said troops attacked the neighborhood from two directions but failed to advance, suffering casualties.

Russia said Friday that U.S. data on the Syrian regime's alleged use of chemical weapons was "unconvincing", and warned Washington against repeating the mistake it made when invading Iraq after falsely accusing Saddam Hussein of stocking weapons of mass destruction.

The Kremlin's top foreign policy adviser Yury Ushakov also said the U.S. decision to provide military aid to Syrian rebels would damage international efforts to end a conflict that has left tens of thousands dead.

NATO Secretary General Anders Fogh Rasmussen on Friday welcomed a "clear" U.S. statement accusing the Syrian regime of using chemical weapons and said Damascus must let the U.N. investigate the allegations.

"I welcome clear U.S. statement. Urgent that Syria regime should let U.N. investigate all reports of chemical weapons use," he said on his official Twitter feed.

U.S. military proposals for arming Syrian rebels include a limited no-fly zone over rebel training camps, the Wall Street Journal reported Friday.

This zone would stretch up to 25 miles (40 kilometers) into Syria, and would be enforced by warplanes flying inside Jordan and armed with long-distance air-to-air missiles, the Journal reported, citing unnamed U.S. officials.

Kuwait now stands at a political crossroads ahead of a crucial court ruling on Sunday on a controversial electoral law, with the decision affecting the future of democracy itself in the oil-rich state.

The constitutional court, whose verdicts are final, will rule whether an amendment decreed by the emir last October to the electoral law is constitutional or not.

President Barack Obama has authorized sending weapons to Syrian rebels for the first time, U.S. officials said Thursday, after the White House disclosed that the United States has conclusive evidence President Bashar Assad's government used chemical weapons against opposition forces trying to overthrow him.

Obama has repeatedly said the use of chemical weapons would cross a "red line," suggesting it would trigger greater American intervention in the two-year crisis.

The six contenders for Iran's next president issued a joint appeal for calm Friday as officials extended polling hours in the first election since outgoing President Mahmoud's Ahmadinejad's 2009 re-election sparked mass protests.

Polling stations remained open four hours longer than initially scheduled as officials reported a turnout almost as large, or bigger, than that for the controversial vote of four years ago.

The United Nations urged Austria on Thursday to prolong the withdrawal of its peacekeeping troops from the Golan Heights until the end of July to allow it to find replacements.

Austria had been the leading contingent in the UNDOF force, which oversees the ceasefire line between war-torn Syria and the Israeli-occupied Golan, but has announced plans to withdraw its force as violence mounts.

Saudi King Abdullah bin Abdul Aziz cut short his vacation in Morocco and decided to return to the kingdom on Thursday evening.

The monarch and his entourage have already left Morocco, according to information obtained by Naharnet.