An estimated 40,000 people have fled a town in eastern Syria after three days of heavy fighting, the United Nations food agency said.
The World Food Programme said on Friday it had delivered additional rations to the area in recent days, adding: "A WFP team visited the area and estimated that around 40,000 people have fled Shaddadeh to Hassakeh city."
Rebels seized Shaddadeh in the country's oil-producing east on Thursday after the fighting, which killed 30 of their fighters and 100 Syrian troops, a violence monitoring group said.
Northeastern Syria was hit by four years of drought before the revolt against President Bashar al-Assad started nearly two years ago, resulting in high rates of malnutrition among children, WFP spokeswoman Elisabeth Byrs said.
"The fighting and displacement only aggravates the misery of these people," she said, adding the agency had sent extra
rations to the area this week.
Taking Shaddadeh brings the rebels closer to the provincial capital Hassakeh, 45 km to the north in the surrounding Hassakeh province.
Omar Abu Laila, a commander in the armed opposition, said army garrison guarding a nearby gas field, al-Ghabsa, had fled as the rebels advanced from the Euphrates river toward Shaddadeh.
"Shaddadeh and Ghabsa are now under our control. In the next few days we will advance toward the city of Hasakah," Abu Laila said by telephone from eastern Syria.
The new wave of displacement adds to an estimated 2.5 million people already uprooted within Syria, many living in squalid conditions in schools and other public buildings converted into shelters, according to the UN.
In the northern Aleppo city, activists reported renewed fighting between regime forces and rebels, as the opposition attempted to gain control of the international airport and a major military base nearby.
"The army shelled the area around Aleppo international airport and Nayrab air base on Friday morning, while rebels used homemade rockets to shell Nayrab," Rami Abdel Rahman, the director of the Britain-based Syrian Observatory for Human Rights, said.
He said at least 150 rebels and government troops have been killed in the battles near the airport on Wednesday and Thursday. The death toll was almost evenly divided between opposition fighters and regime soldiers, the Observatory claimed.
On Wednesday, rebels captured most of the "Brigade 80" force that is in charge of protecting the airport area.
"The army is preparing a large-scale operation to take back control of Base 80," Abdel Rahman said.
Rebels in Aleppo said they shifted focus weeks ago from the city to airbases in the province.
Opposition fighters see the capture of airports such as Al-Jarrah, also in Aleppo province, a few days ago as a way to seize large amounts of ammunition and to put out of action warplanes used by the regime air force to bombard rebel-held areas.
Regime tanks, meanwhile, shelled the town of Khan Sheykhun in the province of Idlib, killing at least 11 civilians, said the Observatory.
In Damascus, the army shelled the eastern district of Jobar, where rebels have set up enclaves.
Friday's violence came a day after at least 155 people were reportedly killed across Syria.
The UN says almost 70,000 people have been killed in Syria's 23-month conflict.