More than 100 cargo vessels have reached Syria in the past few weeks, in the biggest buildup in shipping for over a year as Russia steps up its support for ally President Bashar al-Assad.

The ships have arrived directly from Russia, Black Sea ports such as Constantza in Romania as well as from Lebanon and Egypt, according to shipping data, maritime intelligence and international trade sources.

They say the cargo includes supplies to bolster the offensive as well as grain and sugar to feed those involved in the deepening conflict. Reuters was not able to independently confirm what was in the ships.

Russia has not issued any orders for the delivery of goods to Syria, a Russian government spokeswoman said.

Some deliveries were to fulfil orders made by the Syrian and Russian governments while others were private suppliers, expecting an opportunity to sell their goods as fighting picks up, the sources said.

"Ships are backed up and the logistics of bringing cargoes is complex and chaotic at the moment. We are seeing all of this due to Russia's bigger involvement," a Middle East based commodities trade source said.

The cost of freight to Syria on a container ship jumped in the past two weeks by 25 percent to over $80 a tonne, he said.

Syria's five-year civil war has escalated since Russian jets started air strikes against rebels battling Assad on September 30 after increasing its presence in mid September with extra forces at its naval base at the port of Tartous and at a coastal airstrip.

There were just seven ships arriving at Tartous in late August, but this had jumped to 29 in the week of October 12, according to data collated by UK-headquartered maritime technology company Pole Star. It showed 95 ships arrived at Tartous between mid-September and October 21.

In the other main port of Latakia, ship arrivals peaked during September with a total of 34 ship arrivals in the period from mid September to October 21, Pole Star data showed.

Separate tracking data on Thomson Reuters Eikon showed that since the middle of September at least 60 ships arrived at Latakia and Tartous.

It is common to have variations in vessel data, as not all ships are picked up by every tracking system.

The last time there was intense maritime activity in Syrian waters in a short space of time was in early 2014 when Russia bolstered supplies to Assad to support a previous push by his forces to curb the insurgency. At that time between late December and January an estimated 25 ships arrived in key ports, according to Thomson Reuters Eikon data.

Shipping activity has fallen since the start of the conflict with ship arrivals to Tartous over the past year averaging around 10 vessels a week and 6 vessels to Latakia, according to estimates from another maritime tracking source.

The fighting combined with Western sanctions imposed on Syrian state companies that run the ports as well as multiple local shipping firms have made many international shippers and transporters nervous of sending ships to Syria.

SUGAR AND FUEL

The sources said food, fuel, equipment and military supplies was the most likely cargo on the recent wave of ship arrivals.

One trade source said shipments of raw sugar had also spiked in the past three weeks after months of slow imports.

Russia has stepped up humanitarian shipments of grains to Syria, supplying 71,000 tonnes since the start of the current marketing year on July 1, according to export data cited by Igor Pavensky, deputy head of strategic marketing at rail infrastructure operator Rusagrotrans. This represents 88 percent of its exports to the country for the whole previous 2014/15 season, he said.

An international arms industry source with knowledge of Middle Eastern weapons movements, said equipment has been moved into the area by Russia including ammunition, heavy weapons, bombs, electronic equipment, listening devices and jamming devices. This was mostly transported by ship but also airlifted.

Vyacheslav Davidenkov, spokesman for Russia's arms export monopoly Rosoboronexport said: "We never comment - time, dates, ways and number of deliveries. No comments."

Russia's Northern, Black Sea and Baltic Fleets have also dispatched oil tankers to supply aviation fuel for sorties by Russian air force planes, while a reconnaissance ship had been deployed to monitor communications in Syria and surrounding countries and their territorial waters, Interfax news agency said at the beginning of October, quoting a military source.

A Russian military spokesman declined to comment. – Reuters