Nearly 600 people have been killed in Russian air strikes in Syria nearly a month into Moscow's campaign, two-thirds of them opposition fighters, a monitor said on Thursday.

A total of 595 people have been killed in Russian strikes since September 30, two-thirds of them fighters with opposition forces including the jihadist Islamic State group, the Syrian Observatory for Human Rights said.

The other third, some 185 people, were civilians, including 48 children, the Britain-based monitor said.

Russia has carried out strikes throughout Syria, with only four of the country's 14 provinces untouched by the aerial campaign since it began, according to the group.

The Observatory said it had documented the deaths of 131 IS fighters and 279 other opposition fighters, including moderate and Islamist rebels and members of the Al-Qaeda affiliate Al-Nusra Front.

Russia says its aerial campaign targets IS and other "terrorists" but rebel forces and their backers accuse Moscow of focusing on moderate and Islamist fighters over jihadists.

Several medical groups have also accused Russia of strikes that have hit field clinics and hospitals in Syria.

Russia's air campaign has given new momentum to Syria's ground forces, who have launched offensives in several provinces with air cover from Moscow.

But the offensives have had mixed results.

In the central province of Hama province, the regime has taken several villages but failed to advance much towards a key town on a highway in the region.

And in Aleppo, it has captured at least six villages from rebel forces, along with several hilltops.

But an IS advance meanwhile has severed the only route in and out of the government-held west of Aleppo city.

Russia's intervention in Syria follows that of a US-led coalition that has been carrying out strikes against IS in the country since September 2014.

The US-led coalition does not coordinate with Damascus however.

According to the Observatory, the US-led strikes have killed 3,649 people since they began, around six percent of them civilians.

The monitor said earlier this week that US-led raids had killed 3,276 IS fighters, 147 members of Al-Qaeda affiliate Al-Nusra front or Islamist groups and 226 civilians.

'Increased strikes' kill 35 in Syria hospitals: MSF
Beirut (AFP) Oct 29, 2015 - A "significant increase" of air strikes on Syrian hospitals recently has killed at least 35 patients and medical staff and wounded 72, Doctors Without Borders (MSF) said Thursday.

The group said the escalating attacks began in late September, though it did not identify who was behind them, and that 12 hospitals had been hit in Idlib, Aleppo and Hama provinces, including six supported by MSF.

Russia began an aerial campaign in support of Syria's government on September 30 and has been accused by several other medical groups of hitting hospitals and field clinics since then.

In total, MSF said, "six hospitals were forced to close... and four ambulances destroyed."

"One hospital has since reopened, yet access to emergency, maternity, paediatric and primary health care services remains severely disrupted."

The statement said "tens of thousands of people have been forced to flee their homes" as a result of the attacks.

"After more than four years of war, I remain flabbergasted at how international humanitarian law can be so easily flouted by all parties to this conflict," said Sylvain Groulx, MSF chief for Syria.

In addition to Russia's air strikes, Syria's air force and a US-led coalition targeting the Islamic State group are also carrying out raids in Syria.

In recent days two medical organisations have directly accused Russia of strikes that have hit their medical facilities.

Last week, the Syrian-American Medical Society (SAMS), said an estimated nine Russian air strikes had hit hospitals or field clinics in Syria, including several of its facilities.

Among them was a field clinic in the town of Sarmin in the northwestern province of Idlib, which was hit on October 20, killing 13 people, including a physiotherapist and a nurse, according to SAMS.

And this week, the Union of Medical Care and Relief Organisations NGO said three hospitals it supports had been targeted in air strikes.

One of the facilities, in Latamneh in Hama province had been targeted by Russian strikes on two occasions, killing ten patients and injuring civilians and medical workers, the confederation of medical organisations said.

More than 250,000 people have died in the Syrian war, now in its fifth year.

More than seven million people have been displaced inside the country and another 4.2 million have fled abroad in one of the largest displacement crises of modern times.