BEIRUT -- At least 11,000 Syrians poured into neighbouring countries in a single day, U.N. officials said Friday, in a dramatic surge in the exodus of refugees fueled by heavy battles between regime forces and rebels for control of a border town.

Some of the refugees desperately clambered over razor-wire border fences to reach safety in Turkey, fleeing one of the heaviest battlegrounds -- the town of Ras al-Ayn, where rebels seized security compounds of the regime's most powerful intelligence agencies and regime forces pounded rebels with shelling.

The flood of people was "the highest that we have had in quite some time," said Panos Moumtzis, the U.N. refugee agency's regional co-ordinator for the region.

The escalation -- much more than the average 2,000 to 3,000 Syrians fleeing daily -- brings the number of Syrian refugees registered with the agency to more than 408,000, he said.

Even as the turmoil worsened, Syrian President Bashar Assad said he had no regrets over his regime's crackdown in the 19-month-old uprising against his rule. In an interview with Russian television, he said there was no civil war in Syria, insisting that he was protecting Syrians against "terrorism" supported from abroad.

Syria's conflict began largely as peaceful protests against Assad's rule, but it has since collapsed into civil war after rebels took up arms in response to the regime's bloody crackdown. Rebels have driven regime forces out of much of a pocket of northwestern Syria and battle troops in several large cities and in towns around the country, even as the fight takes on dangerous sectarian tones between a mainly Sunni opposition and a regime dominated by Assad's minority Allawite sect.

More than 36,000 people have been killed in the violence since March 2011, according to activists.

During the 24-hour flood of refugees that began Thursday, 9,000 Syrians fled in to Turkey -- including 70 who were wounded and two who then died, U.N. officials said. Jordan and Lebanon each absorbed another 1,000 refugees.

The largest flow into Turkey came from the fighting at Ras al-Ayn in the predominantly Kurdish northerneastern province of al-Hasaka. The town hugs the border, practically adjacent to the Turkish town of Ceylanpinar.

On Thursday, rebels captured a border crossing between the two towns, Ceylanpinar's mayor, Ismail Aslan, told The Associated Press by telephone.

The next day, rebels overran three security compounds in the town belonging to the Military Intelligence, Air Force Intelligence and General Intelligence Directorate agencies, according to the Britain-based Syrian Observatory for Human Rights, an opposition activist group.

More than 20 soldiers were killed in the fighting, the Observatory said.

Regime forces shelled rebel positions on Friday morning, Ceylanpinar's mayor said. Regime tanks were also moving into the area to join the fight, according to another opposition activist group, the Local Coordination Committees.

Turkey's Anadolu Agency video footage showed Syrians jumping over and climbing through the razor-wiree fence that makes up part of the 911-kilometre (566-mile) border, to cross into Ceylanpinar.

Others fled into Turkey further west along the border, trying to escape fighting at the Syrian town of Harem in Idlib province, which has been the scene of intensified battles in recent days.

The new arrivals bring the number of refugees in Turkey to around 120,000.

Radhouane Nouicer, the U.N.'s regional humanitarian co-ordinator for Syria, said the Middle East nation is seeing unrelenting increases in violence, suffering, displacement and losses "and civilian Syrians continue to pay the price."

He said U.N. officials also worry that in recent weeks Kurds and Palestinians have become increasingly being drawn into the fighting.

Earlier, state-run Anadolu Agency said a group of Syrian soldiers, including two generals and 11 colonels, had fled to Turkey with their families and were taken to a camp that shelters military defectors, including dozens of other generals.

In fighting elsewhere Friday, at least 18 people, including children, were killed when government troops shelled the eastern village of Qouriyeh, the Observatory and the LCC said. An amateur video showed what appeared to be men, women and children, some of them with gapping wounds laying in street in what appeared to be a local market.

Activist videos could not be independently verified due to reporting restrictions in Syria, but they appeared genuine and corresponded to other AP reporting on the events depicted.

A car bomb near the mayor's office in the Damascus suburb of Maadamiyeh killed at least four people, the Observatory said.

Assad's defiant tone in the TV interview aired Friday mirrored the stance he has staunchly taken since his country's crisis began -- that his regime faces terrorists, not a popular uprising, and that he is will not step down. Speaking to English-language Russia Today TV, Assad hinted he will stay in his post until at least 2014 when presidential elections are scheduled to take place.

"I think for the president to stay or leave is a popular issue," he said.

Asked if he has any regrets, he said: "Not now," although he acknowledged that "when everything is clear" it would be normal to find some mistakes.

"We do not have a civil war," Assad said. "It is about terrorism and the support coming from abroad to terrorists to destabilize Syria. This is our war," he said, adding that it was a case of "terrorism through proxies, either Syrians living in Syria or foreign fighters coming from abroad," Assad said.

He said that when foreign countries stop sending arms to rebels, "I can tell (you) that in weeks we can finish everything."

Asked if he accepts that government forces have committed war crimes against their civilians, Assad said "we are fighting terrorism. We are implementing our constitution by protecting the Syrian people."

He referred to attacks by Chechen militants in Russia that killed scores and how Moscow retaliated. "The army in Russia protected the people, would you call it war crimes?! No, you would not," Assad said.

Assad, who came to power after his father and predecessor Hafez died in 2000, spoke in English in the interview that was broadcast in full on Friday. In an excerpt aired a day earlier, Assad said he will "live and die" in Syria and will not leave his country.

Sophie Shevarnadze, the journalist who conducted the 26-minute interview, said during the broadcast that she met Assad in a "newly renovated" presidential palace in Damascus.

She added that she spoke with Assad for about 15 minutes before the interview started and he told her that his three children still go to public schools in Damascus. She added that his British-born wife, Asma, is in Syria as well.

Assad is currently serving his second seven-year term as president, but a new constitution allows him to run again at least twice. The constitution, touted by the regime as a reform, was approved in a referendum earlier this year even as fighting raged. It opens the way for other candidates to run for presidency and imposes a two-term limit on the president, meaning Assad could remain legally in power through 2028.

Most Syrian opposition groups and rebels dismissed Assad's reforms as superficial and say they will not accept anything less than Assad's departure.

Also Friday, the main Syria's main opposition bloc in exile, the Syrian National Council, was debating whether to become part of a single leadership group that would set up a transitional government in rebel-held areas of Syria.

Several senior SNC members said the group is likely to accept the plan in principle, possibly by the end of Friday, but has significant reservations.

Proponents say the plan could give new momentum to the battle to oust Assad.