Russia's military has announced a three-hour daily halt of fighting around Syria's ravaged city of Aleppo to allow humanitarian convoys into the city after Syrian rebels broke a siege by the Russian-backed government of President Bashar al-Assad.

"To guarantee total security for the convoys to Aleppo there will be humanitarian windows established from 1000 to 1300 local time starting tomorrow [Thursday] during which all military hostilities, aviation strikes and artillery strikes will be halted," Lieutenant General Sergei Rudskoy of the Russian army's general staff told journalists on Wednesday.

Rudskoy said that a road had been built to an area on the northern outskirts of Aleppo through the Castello shopping centre to "ensure safety and organise round-the-clock delivery of food, water, fuel, medicine and other necessities to the city's west and east".

The United Nations, which has earlier called for 48-hour weekly pauses for the aid deliveries, said the three-hour truce announced by Russia would not be enough to meet the needs of civilians in the war-battered Syrian city.

"To meet that capacity of need, you need two lanes and you need to have about 48 hours to get sufficient trucks in," UN top aid official Stephen O'Brien told reporters on Wednesday.

O'Brien said he had not been fully briefed on the Russian proposal, but that there were complicated logistics to address, such as ensuring that truck drivers have enough time to safely make the trip to the city and back.

READ MORE: Syrian rebels deny losing ground in Aleppo

"When we are offered three hours, you have to ask what can be achieved in that three hours," said O'Brien.

"Is it to meet the need or would it only just meet a very small part of the need?

Battles rage on

Fighting between government forces and rebels in Aleppo has intensified over the past month, with both sides sending in reinforcements for an all-out battle that could mark a turning point in the five-year war.

A barrage of rocket fire from Syrian rebels killed at least 14 people and left dozens wounded Wednesday in government-held neighbourhoods of divided Aleppo city, state media said.

Fighting struck the southern edges of the battered city Wednesday night as opposition fighters and regime forces gear up for a major protracted battle that could mark a turning point in the five-year war.

Syrian state news agency SANA said rebel fire on the regime-controlled district of Hamdaniyeh on Wednesday killed 13 people and wounded 25 others.

Rocket attacks on another government-held neighbourhood killed one person and wounded 12 others earlier in the day.

SANA said Russian and government planes targeted "terrorist" positions in the city's south, as an AFP journalist in Aleppo said intense air strikes and artillery fire could be heard.

But it was unclear if the major push for control of the city had begun.

Up to two million people in Aleppo have gone without running water for the past four days, UN agencies said, raising the risks of disease in a city already devastated by years of fighting.

Source: Agencies