AMMAN, May 13 (Reuters) - Syrian troops backed by tanks shot dead seven civilians when they overran a rebellious Sunni Muslim village west of the city of Hama on Sunday, activists' organisations said, in a crackdown on the rural epicentre of the 14-month anti-government revolt.

In neighbouring Lebanon, three people were killed when fighting erupted in the city of Tripoli between members of the Alawite minority loyal to Syrian President Bashar al-Assad and members of the Sunni majority.

In the Syrian countryside, at least 27 people were also wounded and scores of houses were burnt in the village of Tamanaa in al-Ghab, the Syrian Network for Human Rights, an opposition activists' group, said.

"The village was subjected to collective punishment. Over half of its houses were burnt. Several people were executed when they were arrested. The rest were killed from bombardment," a statement from the organisation said. It said four women were among those killed.

The attack cast further doubt on the viability of a plan by United Nations and Arab League envoy Kofi Annan for a peaceful solution to the crisis.

Violence by Assad's forces and his increasingly armed foes has continued despite a ceasefire Annan declared a month ago and the presence of a U.N. monitoring mission now with about 150 observers on the ground.

"I think the Annan plan is in crisis and that if the approach of the international community against the violence remains weak, there is a real risk that it will reach an impasse," Burhan Ghalioun, head of the opposition Syrian National Council, said in Rome.

"There must be a plan to exert pressure on the Syrian government. The Syrian regime has not stuck to its commitments. It continues to fire on the civilian population, torture members of the democratic opposition and to sabotage the plan by all means possible," Ghalioun told reporters after meeting Italian Foreign Minister Giulio Terzi.

Opposition leaders are in Rome to try to strengthen their fractured Syrian National Council (SNC), which is seeking international help to oust Assad. Political jockeying within the SNC has prevented it from gaining full international endorsement.

SPILL-OVER

The Syrian Observatory for Human Rights said the army did not appear to have met any resistance when it overran Tamanaa.

Opposition activists said the Sunni Muslim village, one of dozens that have been torched since Assad's forces seized control of the cities of Homs and Hama, had seen regular demonstrations against Assad.

Its defiance had angered the inhabitants of the nearby Alawite village of al-Aziziyeh, a recruiting ground for a militia loyal to Assad known as shabbiha, which participated in a separate assault on Tamanaa on Friday, the activists said.

Tension between the two villages rose after militiamen from al-Aziziyeh killed two youths in Tamanaa on Friday when they opened fire on an anti-Assad demonstration, activists said.

Towns and villages in the region, which is mostly Sunni but has some Alawite areas, have been giving shelter to Syrian Free Army rebels, who have been stepping up their guerilla attacks on the Alawite-led military.

Syria's uprising began as a peaceful protest movement but has become increasingly militarised as rebels fight back against the government's violent crackdown.

In a sign the sectarian tension threatens to spill over into Lebanon, rocket-propelled grenades and automatic rifles were used in the fighting overnight in an Alawite enclave and surrounding Sunni neighbourhoods in the port city of Tripoli, 70 km (45 miles) north of Beirut, witnesses and security officials said.

Syrian troops withdrew from Lebanon under international pressure in 2005 after a 29-year presence. Assad retains significant influence in the country through his main ally, the Shi'ite guerrilla group Hezbollah, the only Lebanese party that has an officially approved arsenal of weapons.

Lebanon's Prime Minister Najib Mikati, a wealthy former businessman who had owned one of Syria's two cellphone operators, is a personal friend of Assad.

Syria's Sunni majority is at the forefront of the uprising against Assad, whose Alawite sect is an offshoot of Shi'ite Islam.

Assad's government says it is fighting a terrorist attempt to divide Syria. It said twin suicide bomb attacks near a secret police branch in Damascus on Wednesday that killed 55 people were the work of foreign-backed Islamist militants.

Jamal al-Wadi, a member of the Syrian National Council, said he believed Assad's security forces were behind the bombings.

"By orchestrating this, the regime is trying to send a message to the outside world that it is facing a terrorist threat, not a popular war against repression," Wadi told Reuters, adding the bombs also served as a warning to the people of Damascus to stop protesting against Assad.

Syrian authorities said on Saturday they had foiled another car bomb attack in Aleppo.

European Union foreign ministers will meet in Brussels on Monday and are expected to impose visa bans and asset freezes on three more individuals in Syria associated with the government's repression. One person will be removed from a list of more than 100 individuals subject to such restrictions and two more companies will also face sanctions, diplomats said.

(Additional reporting by Laila Bassam and Oliver Holmes; Editing by Janet Lawrence)