BEIRUT (Reuters) - Syria's army and its allies have regained an important Aleppo district lost to rebels last month, state media and a war monitor said on Thursday, and were pressing an offensive south of the city to further squeeze the insurgents.

If sustained, the advance in Ramousah would reverse nearly all gains rebels made in a push last month, tighten a blockade over rebel-held eastern Aleppo and ease access for the army into government-held western districts through the city's south.

A second line of attack, aimed at villages south of Aleppo and supported by what a pro-government fighter called "dusk to dawn" bombardment, is intended to isolate Telat al-Eis, a hill captured by rebels in May that commands fire over the region.

However, a rebel source said insurgents still held part of Ramousah and that though the army was mobilizing forces, the Jaish al-Fatah coalition of Islamist groups was still present at the southern Aleppo front.

The battle for Aleppo has become the focus both for President Bashar al-Assad, backed by Shi'ite militias from Iraq and Lebanon, Iran's Revolutionary Guards, and Russian air power, and for the Sunni rebels seeking to overthrow him.

In early August the rebel advance into southern Aleppo gave them control over the residential district of Ramousah, a complex of military colleges immediately to its west and the 1070 Apartment Blocks district west of that.

It opened a corridor into the rebel-held parts of Aleppo that are home to at least 250,000 people and had been under siege for weeks, while forcing the government to access its own areas in the city by a longer, more precarious route.

As international concern has mounted, the United Nations has renewed a call for weekly 48-hour humanitarian ceasefires to allow aid into the city, but efforts by Russia and the United States to agree terms for a truce are dragging.

On Thursday Russian Foreign Minister Sergei Lavrov and U.S. Secretary of State John Kerry discussed by phone potential cooperation to facilitate aid deliveries.

Syria's five-year war has killed hundreds of thousands and displaced 11 million, half of Syria's pre-war population, while drawing in world and regional powers, inspiring jihadist attacks across the world and sparking an international refugee crisis.

BIG REINFORCEMENTS

However, on Thursday the army and its allies "managed to restore control over all of Ramousah district", the Syrian Observatory for Human Rights, a Britain-based monitor of the war that has a network of contacts across the country, reported.

Pro-government al-Mayadeen television showed its reporter speaking from Ramousah, standing near piles of rubble, shell-pocked walls and twisted metal.

"Units of our armed forces in cooperation with allied forces control the gas works, the tannery, the slaughterhouse, the post office and the military checkpoint area of Ramousah in Aleppo," a Syrian military source had said earlier.

Parts of the 1070 district and a school remain in rebel hands, the Observatory said.

State media reported that the government now controlled the road through Ramousah into western Aleppo districts from the south, meaning supplies will no longer have to traverse the narrow strip of army-held land around the city's east and north.

That northern route into the city, the Castello Road, had been the main rebel access point into Aleppo until July when it was taken by the army, putting insurgents under siege.

On Wednesday, an Iraqi Shi'ite militia, the Harakat al-Nujaba, said it had sent an extra 1,000 fighters to southern Aleppo to reinforce positions the army and its allies had taken.

"Big reinforcements arrived from allied groups," the pro-government fighter said.

On Thursday, state media reported jets had attacked rebel positions and movements around the village of Khan Touman, 7 km (4 miles) southwest of Ramousah, which the insurgents seized in May creating a launchpad to break the siege.

(Reporting By Angus McDowall, Leila Bassam and Tom Perry; Editing by Dominic Evans)