HANOVER: President Barack Obama said Monday the US would send up to 250 more special forces and other military personnel to Syria to help rebels fight the militant Islamic State (IS) group.

Obama was in Germany for talks with Chancellor Angela Merkel, and both later met the British, French and Italian leaders to discuss the battle against IS in its self-declared caliphate across northern Syria and Iraq.

In a speech in the German city of Hanover, Obama hailed NATO partners' progress so far in pushing back IS, which he called “the most urgent threat to our nations”.

“A small number of American special operations forces are already on the ground in Syria and their expertise has been critical as local forces have driven ISIL out of key areas,” he said, using an alternative acronym for the militant group.

“So, given the success, I have approved the deployment of up to 250 additional US personnel in Syria, including special forces, to keep up this momentum."

The US forces will not lead the fight on the ground but provide training and advice to local forces against IS, he said.

“These terrorists will learn the same lessons that others before them have, which is: your hatred is no match for our nations, united in defence of our way of life,” said Obama.

Syrian opposition group the High Negotiations Committee (HNC) said boosting the US military presence to about 300 would be “a good step” and help “rid our country of this scourge”.

Escalating violence

While most world powers agree that IS -- which has boasted of beheadings and other battlefield atrocities as well as terror attacks in Paris and Brussels -- must be defeated, they have backed different sides in Syria's complex civil war.

Western powers have offered some support to moderate rebels, while Russia has sent troops and fighter jets to back the government of President Bashar al-Assad.

Syria's conflict, which began in March 2011 with widespread anti-Assad protests, has since spiralled into a multi-front war that has killed 270,000 people.

Aiming to end the bloodshed, all sides eight weeks ago agreed a ceasefire, but it has been frayed by escalating violence around the northern city of Aleppo, with dozens killed by rebel rockets.

At least six people, half of them children, were killed in the bombardment of Aleppo on Monday, civil defence officials and a monitor said.

Three civilians were killed by regime rockets, civil defence said. And another three people died in shelling by rebels, the Syrian Observatory for Human Rights said.

Monday's attacks followed renewed violence in the city that killed at least 26 civilians a day earlier.

Inside the rebel-held east, residents enduring water cuts and a power blackout reported intermittent shelling and rocket fire.

Ground troops 'a mistake'

Obama on Sunday pressed for all parties to return to the negotiating table and “reinstate” the internationally-brokered ceasefire -- the clearest indication yet that the White House believes the truce has all but disintegrated.

Chancellor Angela Merkel said after the five-way meeting in Hanover that all the leaders shared the “concern that the ceasefire is fragile and is at times being dramatically violated”.

Obama, Britain's David Cameron, Francois Hollande of France and Italy's Matteo Renzi had all agreed that the only solution would come through political talks in Geneva, she said.

A Western diplomat said all parties which agreed the truce are committed to maintaining it, “and no member believes the cessation (of violence) to be over."

Obama has come under criticism for his handling of Syria's war, with opponents saying he could have done more to stem the bloodshed.

But the president -- who came to power vowing to withdraw US troops from Iraq and Afghanistan -- has stood firm in his opposition to plunging the United States into another ground war in the Islamic world.

In an interview with the BBC, Obama said that “it would be a mistake for the United States, or Great Britain, or a combination of Western states to send in ground troops and overthrow the Assad regime."