Saudi Arabia's push for a tough stand against its arch-rival Iran is expected to dominate an Arab League summit on Sunday as regional tensions grow over the wars in Syria and Yemen.

Russia's foreign minister has asserted that a suspected chemical attack in the Syrian town of Douma last weekend was fabricated with the help of an unspecified foreign intelligence agency.

Sergey Lavrov says Russian experts have inspected the site of the alleged attack in Douma, just east of Damascus, and found no trace of chemical weapons. He says Moscow has "irrefutable information that it was another fabrication."

At least 25 people were killed and 18 injured in Thursday's bomb attack on funerals for Iraqi fighters killed by jihadists, according to a new toll from police and medics.

Western powers continued to weigh their options on Friday over possible strikes against Syria's regime as pressure built to avoid an escalation following a warning from Russia that military action could lead to "war".

Thousands of Islamist fighters and their relatives left the Syrian town of Douma they once controlled as the last evacuations from Eastern Ghouta continued Friday, a monitor said.

Several thousand Gazans gathered for a third consecutive Friday of mass protests along the border with Israel after violence in which Israeli forces have killed 33 Palestinians and wounded hundreds of others.

The Gulf crisis, which has seen Qatar isolated by Saudi Arabia and its allies, is not on the table at the upcoming meeting of Arab League states, Riyadh's foreign minister said Thursday. 

The British government on Thursday agreed on the "need to take action" alongside the U.S. and France over a chemical weapons attack in Syria, Prime Minister Theresa May's office said.

"Cabinet agreed on the need to take action to alleviate humanitarian distress and to deter the further use of chemical weapons by the Assad regime," Downing Street said after May held an emergency meeting with her top team.

Russia has requested that the U.N. Security Council meet on Friday to discuss the threat of U.S.-led military action in Syria, diplomats said.

The request came after Russian Ambassador Vassily Nebenzia said the priority was to avert U.S.-led strikes on Syria that could lead to a dangerous confrontation between Washington and Moscow.

U.S. Defense Secretary Jim Mattis announced Thursday that his country wants to avoid an “out of control” situation in the event of any military strike on Syria over the suspected Douma chemical attack.

At a congressional hearing on the Pentagon's 2019 budget request, Mattis declined to discuss military plans but said legislative leaders would be notified before any attack was undertaken. He said that because the U.S. had no one at the site of the suspected chemical attack last Saturday, the U.S. has no hard evidence of what happened. But he said he personally believes it was an "inexcusable" use of chemical weapons.