Russia says it has launched rocket strikes on Islamic State group targets in Syria from warships in the Caspian Sea - about 1,500km (930 miles) away.

Defence Minister Sergei Shoigu said four warships fired 26 sea-based cruise missiles on 11 targets, destroying them and causing no civilian casualties.

Meanwhile, Syrian ground troops have launched an offensive under Russian air cover, Syrian officials say.

Russia denies claims that its week of strikes have mainly hit non-IS targets.

The Syrian Observatory for Human Rights reported "the most intense fighting in months" in Hama and Idlib provinces. The clashes followed a wave of Russian air strikes in the same areas, it said.

It appears to be the first co-ordinated offensive since the air campaign by Russia - a staunch ally of Syrian President Bashar al-Assad - began on 30 September.

Russia says it is targeting "all terrorists", but at least some of its air strikes have reportedly hit civilians and Western-backed rebels.

US Defence Secretary Ash Carter said that coalition forces fighting IS in Syria will not co-operate with Russia.

"We believe Russia has the wrong strategy," he said. "They continue to hit targets that are not IS.

"We believe this is a fundamental mistake."

Turkish warning

During a televised meeting with Russian President Vladimir Putin, Shoigu said missiles had destroyed all targets - including command and control centres and ammunition depots - and that there had been no damage to civilian installations.

President Putin praised the Russian military, saying the armed forces were "well prepared".

Later, the Russian defence ministry’s Twitter feed showed footage of cruise missiles being launched, saying they "successfully hit all assigned #ISIS [IS] targets with high accuracy".

Col-Gen Andrey Kartopolov said that the cruise missiles targeted IS and al-Qaeda-linked al-Nusra Front sites, including weapons production plants, command centres, ammunition dumps, fuel depots and training bases in the provinces of Raqqa, Idlib and Aleppo.

A media outlet linked to IS published images of what it said were the remains of a Scud missile bearing Russian writing that hit the outskirts of the city of Tabqa - about 55km (34 miles) west of the IS-held northern city of Raqqa on Wednesday morning.

Shoigu also said that Moscow had "established contacts with our Turkish partners".

This comes after Russia's ambassador to Ankara was summoned three times in response to recent violations of Turkey's airspace.

Turkish President Recep Tayyip Erdogan has warned Russia that any "attack on Turkey means an attack on Nato", referring to the alliance's collective defence doctrine, which commits all members to protect one another.