The head of NATO said on Tuesday the military alliance had plans in place to defend Turkey against attack if needed, as the United Nations chief urged the Syrian regime to declare an immediate truce.

“We have all necessary plans in place to protect and defend Turkey if necessary,” Secretary-General Anders Fogh Rasmussen told reporters before a meeting of the alliance’s defense ministers in Brussels, according to Reuters.


Following Syrian gunfire and shelling, NATO ambassadors threw their support behind Turkey in an emergency meeting last week. Turkish forces have retaliated against the bombardment from northern Syria, where President Bashar al-Assad’s forces are battling rebels.

Meanwhile, U.N. Secretary General Ban Ki-moon on Tuesday urged the Syrian regime to declare an immediate truce to bring an end to the conflict that he said had left 20,000 dead over the last 19 months.


“It is unbearable for the (Syrian) people to continue like this. That is why I have conveyed to the Syrian government (a) strong message that they should immediately declare a unilateral ceasefire,” he said.


He told a joint press conference in Paris with French President Francois Hollande that the reaction he had got from the Syrian government had been to ask what opposition forces would do if the regime called a truce, AFP reported.


“That is exactly what I have discussed and I am in the process of discussing with the member states of the (United Nations) Security Council and the countries in the region,” he said.


Ban urged “the opposition forces to agree to this unilateral ceasefire when and if the Syrian government declares it” and he called on countries supplying arms to either side to stop in order to ease the suffering of the Syrian people.


Meanwhile, a watchdog said on Tuesday that twin blasts at a military base near Damascus by suicide bombers, one driving an bomb-laden ambulance, killed dozens of people while the fate of prisoners held there is unknown.


The attack, the latest in a spate of assaults on Syrian military and government installations, was claimed by al-Qaeda-linked al-Nusra Front, which said it was to avenge Muslims “oppressed or killed” by the regime.


“Dozens of people were killed in two suicide attacks against the air force intelligence branch in Harasta” late on Monday, Syrian Observatory for Human Rights director Rami Abdul Rahman told AFP, referring to a town just northeast of the capital.


“The fate of hundreds of prisoners being held in the basements of the (building) is still unknown.”


“The regime has not said a word about what happened last night,” added Abdul Rahman.


“I hold the regime responsible for the fate of the prisoners. They shouldn't be holding all of these people in the first place.”

The Observatory said in an earlier statement that Syrian regime artillery hammered Harasta as well as other rebel belts across the country from dawn on Tuesday.

Al-Nusra Front, which was unknown before the start of the revolt against Assad’s regime but which now regularly issues statements claiming suicide attacks in Syria, said it was behind the Harasta attack.

“In revenge for those who have oppressed or killed Muslims, the decision was taken to strike the Air Force intelligence branch in Harasta,” al-Nusra said in a statement posted on jihadist online forums.


The group described a three-phase operation in which a suicide bomber drove a car loaded with nine tons of explosives to the front of the building, and 25 minutes later, another fighter drove through in a booby-trapped ambulance.


The militants then targeted the area with mortars, according to the statement.


The attack sparked intense fighting between rebels and the army, which at daybreak pounded the town with shells, the Britain-based Observatory said.


It said Syrian forces on Tuesday also rained shells down on rebel strongholds in the second city of Aleppo, which has been fiercely contested since mid-July, and in Idlib province near the Turkish province.


The army also kept up a siege of rebel neighborhoods of the city of Homs – Syria’s third largest -- and the nearby town of Qusayr, sources on both sides said.


“The army is in the midst of trying to cleanse the last rebel districts of the city of Homs,” a Syrian army commander told AFP.


“The army has already cleansed the villages surrounding Qusayr, and is now trying to take back the town itself,” the commander said, speaking on condition of anonymity.

A security official told AFP the army hopes to retake the besieged areas by the end of the week to free up troops for battle zones in the north, such as Aleppo.


Homs province has suffered some of the worst bloodshed and destruction of the uprising which erupted against Assad’s regime in March last year, but since July the main focus of the conflict has shifted to Aleppo, the northern metropolis of some 1.7 million people.