BEIRUT- The Syrian government's powerful Lebanese ally Hezbollah has declared victory in the Syrian war, dismissing remaining fighting as "scattered battles", a pro-Hezbollah newspaper reported on Tuesday.

The comments by Hezbollah leader Sayyed Hassan Nasrallah mark one of the most confident assessments yet by the government side as it regains swathes of territory in eastern Syria in a rapid advance against Islamic State.

Referring to President Bashar al-Assad's opponents, Nasrallah said "the path of the other project has failed and wants to negotiate for some gains", the al-Akhbar newspaper cited him saying at a religious gathering.

"We have won in the war (in Syria)...and what remains are scattered battles," said Nasrallah, whose Iran-backed group has sent thousands of fighters to Syria to support Assad.

A source familiar with the contents of Nasrallah's speech confirmed al-Akhbar's report.

Backed by Russia and Iran, Assad has crushed numerous pockets of rebel-held territory in the western Syrian cities of Aleppo, Homs and Damascus over the last year, and he appears militarily unassailable in the six-year-long conflict.

Ceasefires brokered by Russia, Turkey, Iran and the United States in remaining rebel-held areas of western Syria have freed up manpower on the government side, helping its advance east into the oil-rich province of Deir al-Zor.

The eastward march to Deir al-Zor, unthinkable two years ago when Assad seemed in danger, has underlined his ever more confident position and the dilemma facing Western governments that still want him to leave power in a negotiated transition.

Government forces last week reached Deir al-Zor city, the provincial capital on the Euphrates River, breaking an Islamic State siege of a government-held enclave and a nearby air base.

In a televised speech last month, Assad said there were signs of victory in the war, but that the battle continued.

U.S.-backed militia fighting under the banner of the Syrian Democratic Forces (SDF) have in recent days launched a separate offensive against Islamic State in Deir al-Zor province.

The SDF, which is dominated by the Kurdish YPG militia, is also waging a campaign to capture Raqqa city from Islamic State. It has avoided conflict with the Syrian government.

(Writing by Tom Perry; Editing by Angus MacSwan) ((thomas.perry@thomsonreuters.com; Reuters Messaging: thomas.perry.reuters.com@reuters.net))