Gunmen in inflatable dinghies attacked a military unit on Syria's Mediterranean coast, state media said on Saturday, the first seaborne assault in a 13-month-old uprising against President Bashar al-Assad.

The nocturnal raid, along with the killings of at least 15 people in violence in two areas near the capital Damascus, underlined the threadbare state of a two-week-old, UN-brokered ceasefire accord.

The official SANA news agency said several gunmen and soldiers were killed in a firefight that followed the coastal attack near the northern port of Latakia, 35 km south of the Turkish border.

'The fighting ... resulted in the death and wounding of a number of military personnel while the number of those killed from the terrorist group was not known because they attacked the military unit at night,' SANA said. It did not state the nationality of the attackers.

Damascus has accused Turkey of allowing weapons and funds to flow to insurgents throughout the uprising, the latest in a wave of revolts across the Arab world against autocratic rule. Turkey also plays host to the leadership of the rebel Free Syrian Army.

Lebanese authorities, meanwhile, found weapons including rocket-propelled grenades and rifles on board a ship intercepted in the Mediterranean which may have been trying to supply Syrian insurgents, security sources said.

In a village north of Damascus where army defectors had taken refuge, activists said Syrian forces killed at least 10 people. And overnight, five members of the security forces were killed in an explosion targeting two vehicles near Damascus, the UK-based Syrian Observatory for Human Rights said.

The United Nations says Syrian forces have killed 9,000 people since the start of the revolt in March 2011. Syrian authorities blame foreign-backed militants for the violence and say 2,600 soldiers and police have been killed.

Most independent media have been barred from Syria, making it hard to verify accounts of events on the ground.

The April 12 ceasefire arranged by UN-Arab League envoy Kofi Annan has only modestly reduced the degree of daily carnage, with both sides accusing each other of multiple breaches of the truce.

On Friday, a suicide bomber killed nine people including security officers at a Damascus mosque.

There was no immediate claim of responsibility. The blast was close to the site of a January 6 suicide bombing later claimed by a previously unknown, anti-Assad Sunni Islamist group calling itself the al-Nusra Front.

The latest suicide attack was just one of five explosions to hit the capital on Friday, leading to suggestions that insurgents may be changing tactics and embarking on a sustained bombing campaign aimed at the seat of Assad's power.

'The action is picking up and it seems the (rebels) and Assad's forces are starting to battle it out in Damascus as well,' said one activist based in the capital who uses the name Mar Ram.

UN Secretary-General Ban Ki-moon accused Damascus on Thursday of breaking its pledge to withdraw heavy weapons and troops from towns, saying he was 'gravely alarmed by reports of continued violence and killing in Syria'.

The White House also said it was disappointed at the Damascus government's failure to adhere to its promises and said Washington would 'continue to ramp up the pressure against the Assad regime'.

Russia, one of Assad's biggest remaining allies, said the rebels were largely to blame for ceasefire violations and accused them of seeking to provoke foreign intervention.

'This truce has not yet fully set in largely because opposition armed groups try to create provocations - explosions, terrorist acts, shooting at government forces, government buildings, administrative buildings,' Foreign Minister Sergei Lavrov said.

UN monitors are trickling in and officials say 30 of a planned 300-strong mission should be in place by Monday to reinforce observers already stationed in anti-Assad hotbeds such as Idlib, Hama, Homs and Deraa.

The slow build-up, more than two weeks after the truce came into effect, has been derided by Assad's foes and intensified frustration in Western capitals, where leaders want tough measures imposed on Damascus sooner rather than later.

France says that if Assad's forces do not return to barracks, it will push next month for a 'Chapter 7' UN Security Council resolution - which could allow action ranging from economic sanctions to military intervention.

Russia and China have made clear that they would veto Libya-style military action and have resisted the idea of sanctions.-Reuters