DAMASCUS — The Syrian government accused rebels of using chemical weapons Saturday and warned the United States not to launch any military action against Damascus over an alleged chemical attack last week, saying such a move would set the Middle East ablaze.
The accusations by the regime of President Bashar Assad against opposition forces came as an international aid group said it has tallied 355 deaths from a purported chemical weapons attack on Wednesday in a suburb of the Syrian capital known as Ghouta.
Syria is intertwined in alliances with Iran, Lebanese Hezbollah guerrillas, and Palestinian militant groups. The country also borders its longtime foe and US ally Israel, making the fallout from military action unpredictable.
Violence in Syria has already spilled over the past year to Lebanon, Turkey, Iraq, and the Israeli-occupied Golan Heights. Battle-hardened Hezbollah fighters have joined the combat alongside Assad’s forces.
Meanwhile, US naval units are moving closer to Syria as President Obama considers a military response to the alleged use of chemical weapons by Assad’s government.
US defense officials told the Associated Press that the Navy had sent a fourth warship armed with ballistic missiles into the eastern Mediterranean Sea but without immediate orders for any missile launch into Syria. The officials spoke on condition of anonymity because they weren’t authorized to discuss ship movements publicly.
Obama emphasized that a quick intervention in the Syrian civil war was problematic, given the international considerations that should precede a military strike. He met at the White House on Saturday with his national security team to discuss the next steps in Syria.
US intelligence officials are still trying to determine whether Assad unleashed a deadly chemical weapons attack against his people earlier this week. Officials have said Obama will decide how to respond once the facts are clear.
A statement from the White House about Saturday’s meeting said Obama also received a detailed review of the range of options he has requested for the United States and its international partners if it is determined that Assad has engaged in deadly chemical warfare.
The White House said that Obama and British Prime Minister David Cameron discussed the situation in Syria by telephone Saturday.
Syria’s information minister, Omran al-Zoubi, dismissed the possibility of an American attack, warning that such a move would risk triggering more violence in the region.
‘‘The basic repercussion would be a ball of fire that would burn not only Syria but the whole Middle East,’’ Zoubi said in an interview with Lebanon-based Al-Mayadeen TV. ‘‘An attack on Syria would be no easy trip.’’
In Tehran, Iran’s Foreign Ministry spokesman, Abbas Arakji, warned that an American military intervention in Syria will ‘‘complicate matters.’’
‘‘Sending warships will not solve the problems but will worsen the situation,’’ Arakji said in comments carried by Iran’s Arabic-language TV Al-Alam. He added that any such US move does not have international backing and that Iran ‘‘rejects military solutions.’’
In France, Doctors Without Borders said three hospitals it supports in the eastern Damascus region reported receiving roughly 3,600 patients with ‘‘neurotoxic symptoms’’ over less than three hours on Wednesday morning, when the attack in the eastern Ghouta area took place.
Of those, 355 died, the Paris-based group said.
The Britain-based Syrian Observatory for Human Rights said Saturday that its estimated death toll from the alleged chemical attack had reached 322, including 54 children, 82 women, and dozens of fighters. It said the dead included 16 people who have not been identified.
The group said it raised its death toll from an earlier figure of 136, which had been calculated before its activists in the stricken areas met doctors, residents and saw medical reports. It said the dead ‘‘fell in the massacre committed by the Syrian regime.’’
Death tolls have varied wildly over the alleged attack, with Syrian antigovernment activists reporting between 322 and 1,300 killed.
Zoubi blamed the rebels for the chemical attacks in Ghouta, saying that the Syrian government had proof of their responsibility but without giving details. ‘‘The rockets were fired from their positions and fell on civilians. They are responsible,’’ he said.
With the pressure increasing, Syria’s state media accused rebels in the contested district of Jobar near Damascus of using chemical weapons against government troops Saturday.
State TV broadcast images of plastic jugs, gas masks, vials of an unspecified medication, explosives, and other items that it said were seized from rebel hideouts Saturday.
One barrel had ‘‘made in Saudi Arabia’’ stamped on it. The TV report also showed medicines said to be produced by a Qatari-German medical supplies company. Qatar and Saudi Arabia are strong supporters of the Syrian rebels. The report could not be immediately verified.
An army statement issued late Saturday said the discovery of the weapons ‘‘is clear evidence that these gangs are using chemical weapons against our people and soldiers with help from foreign sides.’’
The claims could muddy the debate about who was responsible for Wednesday’s alleged gas attack, which spurred demands for an independent investigation and renewed talk of potential international military action if chemical weapons were used.
Just hours before the state media reports, the UN disarmament chief arrived in Damascus to press Assad’s regime to allow UN experts to investigate the alleged attack. The regime has denied allegations it was responsible.
The United States, Britain, France, and Russia have urged the Assad regime and the rebels fighting to overthrow him to cooperate with the United Nations and allow a team of experts already in Syria to look into the latest purported use of chemical agents.
The UN secretary-general dispatched Angela Kane, the high representative for disarmament affairs, to push for a speedy investigation into the purported attack. She did not speak to reporters upon her arrival in Damascus on Saturday.