The first civilian deaths since a ceasefire took effect in Syria were reported Thursday, while opposing sides in the conflict continued to hold back aid deliveries to hundreds of thousands of people.

The Syrian Observatory for Human Rights reported the casualties, saying they were two children. One was killed in al Hader in the northern countryside of Queintra, when opposition rebels fired shells on the area. The other was killed by a sniper in the regime-held area of al Masharqa in western Aleppo.

Earlier, the United Nations Syria envoy Staffan de Mistura put most of the blame for the delay in aid delivery on the government of President Bashar al-Assad, which has not yet provided any so-called facilitation letters required by aid trucks to access civilians in need across the country.

"This is something that is required to take place immediately," he told reporters in Geneva.

The truce, brokered by the United States and Russia, has been largely holding since Monday, but 40 aid trucks with supplies are being held up on the border with Turkey, De Mistura said.

There appeared to be some positive movement, however, when Syrian government forces started to withdraw from the Castello Road, a key route to the besieged rebel-held eastern part of Aleppo. Russian monitors are in the area.

"Finally, the Syrian government is fully ready for withdrawing troops from Castello Road, simultaneously with the opposition, to ensure safe passage of UN humanitarian convoys," Russian Defense Ministry spokesman General Igor Konashenkov was quoted as saying by state news agency TASS.

"We do not know if this is a real withdrawal or repositioning," said the Observatory, but confirmed the Russian information and noted this could pave the way for aid to reach people inside.

The rebels themselves have voiced strong opposition to letting in aid via the Castello route, fearing this would end up favouring the government and cementing its control over the road, allowing al-Assad's forces to reintroduce a siege in the future.

Up to 275,000 people in east Aleppo have been cut off from assistance since early July. Overall, 600,000 Syrians are living in besieged or hard-to-reach areas, according to the UN.

De Mistura noted that even the Russians were expressing frustrations with the Syrian government over its blockade.

Contrary to the rest of Syria, aid convoys will not need government pre-approval for accessing the rebel-held eastern part of Aleppo. De Mistura said he expected Damascus to honour this rule, and to let trucks pass without removing medical supplies this time.

He also noted that rebel-controlled local authorities have yet to guarantee unhindered deliveries of aid. The Russians accused rebels of violating the ceasefire and Konashenkov said that "only the Syrian military is observing the truce."

The Observatory, meanwhile, raised the death toll from airstrikes by unidentified planes on an Islamic State-controlled area in Deir al-Zour in eastern Syria to 23, among them nine children.

Islamic State affiliated Amaq news agency also reported the strike, blaming Russia.

Both Russia and the United States consider Islamic State and al-Qaeda fair targets during the truce, and neither extremist organization signed on to the cessation of hostilities.

Konashenkov blamed the US for "its failure to honour its part of the commitments, especially on disengaging the moderate opposition." The US, which supports some moderate rebel factions, is working to solve this issue.

Rebel groups fight alongside al-Qaeda-linked militants against al-Assad's forces, as the extremists are among the most potent fighting forces in the country. The US has said the rebels will soon need to separate themselves from the extremists.

More on this story

Aid delayed for hundreds of thousands of Syrians as ceasefire holds

A ceasefire in Syria was holding Thursday, despite a limited number of reported breaches, but humanitarian aid supplies have not yet entered the country and are being held up on the border with Turkey.

Related stories

Latest news

Plane crashes at airport in Melbourne

A five-passenger charter plane has crashed into a building next to Essendon Airport in Melbourne, with witnesses reporting explosions, fire and black smoke, police said Tuesday.

Air France pilots give green light to lower cost subsidiary

Members of Air France's main pilots union on Monday voted to accept the creation of a new lower cost subsidiary that the flag carrier hopes will help it compete on long-haul routes.

US Army General McMaster tapped as Trump's national security advisor

Army Lieutenant General HR McMaster will be the new White House national security advisor, US President Donald Trump told reporters Monday.

Greece's creditors want sweeping reforms before next bailout payment

Greece must make sweeping reforms to its labour market, pension system and collective bargaining agreements in order to receive its next vital bailout payment, the country's European creditors said Monday.

President wants to recall "politically appointed ambassadors", can't do it without gov't

President Kolinda Grabar-Kitarovic said that many politically appointed Croatian ambassadors were not carrying out state policies but that she could not replace them without the government to appoint career diplomats who would fight for Croatia's interests.

Izetbegovic hopes ICJ will confirm Serbia's responsibility for genocide

The Bosniak member of the tripartite presidency of Bosnia and Herzegovina, Bakir Izetbegovic, on Monday rejected criticism stirred up by the announcement that the International Court of Justice (ICJ) would be requested to review its judgement made after Bosnia sued Serbia for genocide.

British lawmakers locked in heated debate over Trump's state visit

Allowing US President Donald Trump to visit Britain would be akin to "pimping out the Queen," one British lawmaker said Monday during a heated debate in British parliament over two petitions concerning the US leader's future state visit.

Vitaly Churkin, Russia's sharp-tongued ambassador to the UN, dies

Russia's long-time ambassador to the United Nations, Vitaly Churkin, died in New York on Monday, following a career that spanned four decades and saw Russia emerge from the Soviet Union and experience many turbulent events in its relations with the West.

French police raid National Front over European Parliament payments

France's far-right National Front Monday said that investigators had searched its offices in relation to allegations that it misused European Parliament funds.

Unhappy Presidents' Day: Trump still manoeuvring after Sweden comment

Donald Trump used his first Presidents' Day in office to continue trying to talk his way out of comments implying a terrorist attack in Sweden that never happened.

Croatia supports Kosovo's territorial integrity - Grabar-Kitarovic

Croatia's President Kolinda Grabar-Kitarovic on Monday expressed the support to Kosovo's territorial integrity and Euro-Atlantic aspirations during her talks with the visiting Kosovo Foreign Minister Enver Hoxhaj.

Petrov rules out early parliamentary election

Parliament Speaker and Bridge party leader Bozo Petrov on Monday dismissed speculation about a reshuffle of the parliamentary majority, saying an early election was likelier, but that right now he did not see "such a scenario."