Syria’s new president Ahmed al-Sharaa has vowed to “pursue the criminals who shed Syrian blood and committed massacres and crimes” in his first address to the nation since the fall of ousted leader Bashar al-Assad.

Sharaa has been named president for a “transitional period”, seven weeks after he led the rebel offensive that overthrew Assad.

He committed to issuing a “constitutional declaration” to serve as a “legal reference” during the country’s transition, following the suspension of the old constitution.

Earlier, rebel military commander Hassan Abdul Ghani announced the cancellation of Syria’s 2012 constitution and the dissolution of the former regime’s parliament, army and security agencies, according to the Sana news agency.

In a pre-recorded speech, Sharaa vowed to “pursue the criminals who shed Syrian blood and committed massacres and crimes”, whether they were in Syria or abroad, and to establish “real transitional justice” after Assad’s fall.

He promised to hold a “national dialogue conference” and vowed to preserve “civil peace” and Syria’s territorial unity.

It comes after announcements were made on Wednesday during a event in Damascus attended by the commanders of factions who fought alongside the rebel alliance led by Sharaa’s Islamist group, Hayat Tahrir al-Sham (HTS). It was entitled the “Conference for Announcing the Victory of the Syrian Revolution”.

All rebel groups which opposed Assad in the 13-year civil war would be dissolved and integrated into state institutions, Sharaa said.

As president, Sharaa would form an interim legislative council to help govern until a new constitution was approved, Ghani said.

In late December, Sharaa told Al Arabiya TV in an interview that it would take up to four years to hold new elections.

He said an up-to-date census would be required first which “would take time” and that writing up a new constitution would also take up to three years to complete.

Sharaa also reiterated in the interview that he planned a “national dialogue conference”, which he said would “bring together all components” of Syrian society.

In 2011, Assad brutally crushed a peaceful pro-democracy uprising, sparking a civil war in which more than half a million people were killed and 12 million others forced to flee their homes.

HTS – a former al-Qaeda affiliate that is still designated as a terrorist organisation by the UN, the US, the EU and the UK – previously dominated the last rebel stronghold in north-western Syria.

On 8 December, as the rebels entered Damascus after routing the army and sweeping down from the north in the space of only 12 days, Assad resigned the presidency and fled to Russia.

An interim government led by Mohammed al-Bashir, the former head of the rebel administration in the north-west, has been tasked with running the country until March.

Earlier on Tuesday, the Syrian government called on Russia to address “past mistakes” by paying war reparations, during the first visit by a top Kremlin delegation since the fall of Assad, its staunch ally.

Sharaa and Russian Deputy Foreign Minister Mikhail Bogdanov discussed “rebuilding trust with the Syrian people through concrete measures such as compensation, reconstruction and recovery”, Sana reported.

The Russian foreign ministry said its delegation expressed “unwavering support” for Syria’s unity and readiness to assist its recovery from the civil war.

The Russian military carried out tens of thousands of air strikes on rebel-held areas after intervening in the conflict in support of Assad in 2015. A UK-based monitoring group says more than 21,000 people, including 8,700 civilians, were killed by those strikes and other Russian operations.

Since the fall of the Assad regime, Russia has been withdrawing troops and weapons from its two bases on Syria’s Mediterranean coast – Hmeimim airbase near Latakia and the naval base in Tartous.

Recent satellite photos analysed by BBC Verify showed that two Russian warships were docked at Tartous, which experts said suggested an evacuation of the facility had begun.

However, Russia is believed to be seeking to retain both bases, which give it a strategically important foothold in the eastern Mediterranean.

Following the Russian delegation’s visit to Damascus, Kremlin spokesman Dmitry Peskov told reporters in Moscow: “That was an important trip, and the contacts were important, too, because it is necessary to establish and maintain a constant dialogue with Syria.”

When asked about reports that the Syrian government had requested Assad’s extradition and war reparations in return, he replied: “I leave this without any comments. We will continue further dialogue with the Syrian authorities.”

In the interview with Al Arabiya, Sharaa noted the “deep strategic interests between Russia and Syria” and said he did not want Russia to leave “in a way that undermines its relationship with our country”.

“All of Syria’s arms are of Russian origin, and many power plants are managed by Russian experts,” he added.