DAMASCUS — Syrian troops backed by tanks clamped down Monday on the flashpoint province of Homs, a day after gunboats joined an assault that killed more than 20 people in Latakia city, activists said.

As the country's anti-regime uprising turned five months old, the Syrian Observatory for Human Rights said snipers shot dead an old man in the provincial town of Hula and reported another killing in Latakia.

"The community of Hula is under siege ... The army is carrying out raids and arrests under the cover of heavy gunfire" in Homs province, said the Britain-based rights group.

Another rights monitoring group said "a large number of tanks entered Hula this morning."

"Security agents encircled all the entrances to Hula and they started shooting to terrify local residents. Then the army went in to make raids and arrests," said the Observatory.

The operation came a day after gunboats joined the pounding of the port city of Latakia that killed as many as 26 people, in the first attack from the sea since Syria's anti-regime revolt erupted March 15, according to activists.

Many residents were allowed to flee the worst-hit districts of Latakia at dawn on Monday, but soldiers opened fire at a checkpoint, killing a man and wounding five other people, the Observatory said.

In the eastern city of Deir Ezzor, security agents unleashed a wave of arrests while a 67-year-old man succumbed to his wounds after being shot on Friday in a city centre street, the Observatory said.

"Security agents arrested 27 people during a campaign of arrests across the neighbourhoods of this city and in surrounding villages," it said.

President Bashar al-Assad has appointed a new governor for Aleppo province in northern Syria, the state news agency SANA announced.

The decree followed the naming of new governors for Homs and Hama in the centre of the country as well as for Daraa in the south, scene of the first major bloodshed of the uprising.

SANA also ran a denial that the navy had attacked Latakia, however, quoting its correspondent in the Mediterranean city as saying security forces had battled gunmen.

Activists said four more people were killed elsewhere on Sunday.

The Syrian Observatory said at least 23 people died and dozens more were wounded in Latakia, while the National Organisation for Human Rights in Syria (NOHRS) put the Latakia death toll for Sunday at 26.

The Syrian Observatory said the vessels opened up with heavy machine guns.

The NOHRS, backing up the report, gave a list of 26 victims -- including two Palestinian men from the Ramel refugee camp in southern Latakia -- and said one more person was killed in Homs and another in Idlib, northwest Syria.

A spokesman for the UN refugee agency UNRWA, Chris Gunness, said reports from the Ramel camp spoke of "fire from tanks which have encircled the area as well as fire from ships at sea."

SANA denied naval vessels had opened fire on the city. "Law enforcement members are pursuing armed men who are using machine guns, grenades and bombs in Ramel from rooftops and from behind barricades," it said.

The head of medical services in Latakia was quoted as saying that two members of the security forces were killed and 41 others wounded "while chasing armed men."

Spain's El Pais newspaper, meanwhile, reported that Madrid sent a special envoy to Damascus last month to convince Assad to accept a plan to go into exile with his family.

The government was also "ready to offer asylum to Assad and his family in Spain," the country's leading daily said.

"My impression is that (Assad) will not compromise on anything substantial," envoy Bernardino Leon said on his return, El Pais reported. "My (Syrian) interlocutors were totally detached from reality."

On Saturday, US President Barack Obama, Saudi King Abdullah and Britain's Prime Minister David Cameron called for an "immediate" end to the Syrian government's deadly crackdown.

The violence has killed around 2,200 people, including some 400 members of the security forces, according to rights activists. Syrian authorities have blamed the bloodshed on armed gangs and Islamist militants.

The UN Security Council is due to hold a special meeting on Thursday to discuss human rights and the humanitarian emergency in Syria.