In the town of Douma retaken more than a week ago, global chemical weapons experts visited a second site after an alleged toxic gas attack there on April 7.
In Brussels, international donors were expected to pledge $4.4 billion (3.6 billion euros) in aid for Syrians, a senior UN official said.
Seven years into the civil war, President Bashar al-Assad's regime has ramped up efforts to secure the capital with backing from ally Russia.
The regime took control of Eastern Qalamun northeast of the capital on Wednesday, state media said, after the last rebels left on buses under an evacuation deal.
At the same time, regime air strikes and rocket fire pounded southern areas of the capital held by the Islamic State jihadist group after regime raids there killed six civilians overnight.
The retaking of Eastern Qalamun follows the latest in a string of deals between opposition fighters and the regime for rebels to withdraw from areas near the capital.
"The operation to bring terrorists with their families out of the areas of Eastern Qalamun has ended and the region is free of terrorism," state television said, using its usual term for rebels.
Government security forces entered the region's town of Al-Ruhayba, some 60 kilometres (35 miles) northeast of Damascus, after the last rebels departed, it said.
Earlier this month, Assad's forces announced their reconquest of the key rebel bastion of Eastern Ghouta east of the capital, after a blistering offensive and evacuation deals that saw thousands of people transferred to northern Syria.
Second 'trauma of displacement'
Rebels withdrew from its main town of Douma last, after medics and rescuers said more than 40 people were killed on April 7 in an alleged chlorine and sarin attack in the town.
Damascus has rejected the accusations as "fabrications", but invited the global chemical weapons watchdog to visit the town.
"Today, the FFM (fact-finding mission) team carried out a visit to a second location in Douma. It also collected samples at this site," the Organisation for the Prohibition of Chemical Weapons said Wednesday.
On Saturday, the team had visited a first site in the bombed-out town after weeks of delay.
In the south of the capital, regime air strikes late Tuesday killed six civilians in the Palestinian camp of Yarmuk, a Britain-based monitor said.
The latest deaths bring to 19 the total number of civilians killed in regime bombardment on the capital's south since Thursday last week, the Syrian Observatory for Human Rights said.
Yarmuk -- now IS's last urban redoubt in Syria or Iraq -- was once Syria's biggest Palestinian refugee camp, home to around 160,000 people.
But the United Nations' agency for Palestinian refugees, UNRWA, said most of the 6,000 refugees still living in the camp last week have since fled and just a few hundred remain.
UNRWA commissioner-general Pierre Krahenbuhl said Palestinian refugees in Syria were living for the second time in their history as a community "the trauma of displacement".
Yarmuk was set up in 1957 less than a decade after the founding of Israel sent hundreds of thousands of Palestinians fleeing from their homes.
'Population replacement'
Since April 19, at least 61 pro-regime fighters and 49 jihadists have been killed in the capital's southern suburbs, the Observatory says.
There are an estimated 1,000 IS fighters left inside Yarmuk and the adjacent districts of Hajar al-Aswad and Qadam.
IS has lost much of the land it once held after sweeping across large parts of Syria and neighbouring Iraq in 2014, but has managed to stay on in Yarmuk.
More than 350,000 people have been killed and millions displaced since Syria's war started in 2011 with the brutal repression of anti-government protests.
In Brussels, international donors gathered to raise money for humanitarian aid in the war-torn country and for Syrian refugees.
"My best guess is that by the end of the day we will have heard pledges for 2018 of $4.4 billion," Mark Lowcock, the head of UN aid agency OCHA, said.
In northern Syria, a final convoy carrying hundreds of fighters and civilians from Eastern Qalamun was heading to the region of Afrin held by pro-Turkey rebels, the Observatory and a rebel commander said.
Last month, Ankara-led forces seized Afrin from Kurdish fighters whom Turkey considers to be "terrorists", after an almost two-month assault that forced tens of thousands of civilians from their homes.
The Observatory says three of the convoys that have left East Qalamun since Saturday went to the Afrin region.
Syria expert Fabrice Balanche said the new arrivals are tantamount to "population replacement" -- albeit without the regime's agreement.
"Turkey is ousting the Kurds from the region and settling people it considers to be more reliable" there, he told AFP.
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