Updated

Syrian rebels on Friday captured a strategic town near the border with Jordan after a day of fierce clashes that killed at least 38 people, activists said, as opposition fighters expand their presence in the south, considered a gateway to Damascus.

The Britain-based Syrian Observatory for Human Rights said 16 rebels were among the dead in the fighting in and around Dael. The town lies less than 10 miles from the Jordanian border in Daraa province, where the uprising against President Bashar Assad's regime began two years ago.

The rebel gains have coincided with what regional officials and military experts say is a sharp increase in weapons shipments to opposition fighters by Arab governments in coordination with the U.S. in the hopes of readying a push into Assad's stronghold in the capital, Damascus.

Although rebels control wide areas in northern Syria that border Turkey, the Jordanian frontier is only about 60 miles from Damascus, or a third of the distance to the Turkish border.

The battle for Dael came as authorities ordered an investigation into a mortar attack on Damascus University that killed at least 10 students on Thursday, state media said. The attack was the deadliest since a wave of mortar shells began hitting the capital last month, puncturing the sense of normalcy the regime has tried to cultivate in the city.

It was unclear who fired the mortar rounds. The government blamed "terrorists," its blanket term for those fighting Assad's regime. Anti-regime activists accused the regime of staging the attack to turn civilians -- many of whom in Damascus are already wary of the opposition fighters -- against the rebels.

"Rebels now control wide areas in the Daraa countryside,"' said Rami Abdul-Rahman who heads the Observatory. "Every area that goes out of government control is important."

Syrian activist Maher Jamous, who is from Dael but currently lives in the United Arab Emirates, said that despite the steady advances and the latest rebel victory in Dael, the regime still maintains a strong presence in the strategic province that leads to the capital.

Jamous said the capture of Dael increases the pressure on the regime.

The regime is known to have posted elite troops in Daraa province, which separates Damascus from the Israeli-occupied Golan Heights that the Jewish state captured in 1967 and annexed in 1981.

Jamous said Dael has a population of 40,000, making it one of the bigger towns in the primarily agricultural region, which is dotted with small family farms. He added that the town fell briefly into the opposition's hands in the early days of the uprising, but was quickly retaken by regime forces in May 2011.

Amateur videos posted online by activists, showed rebels in the streets of Dael and the bodies of dead soldiers lying on the ground. The videos appeared genuine and corresponded to other AP reporting on the events depicted.

In other areas, the Observatory said heavy clashes were taking place between regime forces and fighters renewing their attempts to storm a strategic military facility, known as the 17th Division base, north of the city of Raqqa that was captured by rebels earlier this month.

The division is considered one of the most important remaining regime strongholds in the northern province that borders Turkey, the Observatory said. It added that warplanes carried out several air raids in the area.

The Observatory said regime forces bombarded the Damascus suburb of Adra, while the government al Al-Ikhbariya TV said troops killed "many terrorists" in the area which is close to one of the main jails in the country.

The Aleppo Media Center and the Observatory reported clashes, shelling and attacks by helicopter gunships near the international airport of the northern city of Aleppo, Syria's largest and commercial center.

Syria's crisis began in March 2011 with protests demanding Assad's ouster. Following a harsh government crackdown, the uprising steadily grew more violent until it became a full-fledged civil war. The U.N. says more than 70,000 people have been killed since.