The Latest: Activists say airstrike kills 4 in eastern Syria

FILE – In this this file photo released on May 4, 2015, on a militant website, which has been verified and is consistent with other AP reporting, Islamic State militants pass by a convoy in Tel Abyad, northeast Syria. Five years of failed efforts to quell the fighting in Syria have persuaded many observers that the war, inconclusive and catastrophic on a historic scale, may be unresolvable. But a closer look at the landscape allows a glimmer of hope that a turning point may have been reached with the truce that took effect Monday, Sept. 12, 2016. (Militant website via AP, File)

BEIRUT (AP) — The Latest on developments in Syria, where a cease-fire brokered by the U.S. and Russia has come into effect (all times local):

3:20 p.m.

Syrian opposition activists say an airstrike on the eastern Syrian town of Mayadeen, which is held by the Islamic State group, has killed at least four people and wounded dozens.

That casualty toll is according to Deir el-Zour 24, an activist collective.

The Britain-based Syrian Observatory for Human Rights, meanwhile, says Thursday’s airstrike killed seven people.

It wasn’t known who carried out the airstrike.

Mayadeen is in the eastern province of Deir el-Zour, near the Iraqi border. IS is not included in the U.S.-Russia-brokered truce that went into effect this week.

The U.S.-led coalition, Russia and the Syrian government have been carrying out air raids against the extremist group.

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1:20 p.m.

The U.N. Syria envoy Staffan de Mistura says “we have a problem” on getting humanitarian aid into Syria, despite the U.S.-Russia brokered deal.

De Mistura says Thursday the Syrian government has not provided needed “facilitation letters” to allow for the start of U.N.-led aid convoys expected under the new cease-fire agreement.

He says 40 aid trucks are ready to move and his priority is getting aid into the embattled, rebel-held neighborhoods of the northern Syrian city of Aleppo.

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1:00 p.m.

Activists say Syria’s cease-fire is still holding despite some violations but aid has not yet reached besieged rebel-held neighborhoods of the northern city of Aleppo.

The Britain-based Syrian Observatory for Human Rights says government forces and opposition fighters are now ready to withdraw from the Castello road, a main artery into Aleppo, to hand it over to Russian troops.

It says Thursday that government forces will not start pulling out until the rebels begin to do the same.

The cease-fire that went into effect Monday is part of a U.S.-Russia agreement that also calls for allowing humanitarian aid to reach besieged areas in Aleppo.

The U.N says some 20 trucks carrying U.N aid and destined for rebel-held Aleppo remained in the customs area on the border with Turkey on Wednesday.