* Syrian tanks shell Hama, violence in other cities
* U.N. chief Ban says Security Council sends clear message
* Rights body details further army abuses
BEIRUT, March 22 (Reuters) - Clashes flared across Syria on Thursday, opposition activists said, a day after the U.N. Security Council had called on all sides to stop fighting and seek a negotiated settlement to the year-long uprising.
U.N. Secretary General Ban Ki-moon said the Council's unanimous statement had sent a clear message to Syria to end all violence, but the appeal had little impact on the ground, where rebels are seeking to oust President Bashar al-Assad.
Opposition sources said Syrian tanks had heavily shelled a large neighbourhood in the city of Hama on Thursday after fighting between Free Syrian Army rebels and pro-Assad forces.
The shelling destroyed houses in the Arbaeen neighbourhood of northeast Hama, which has been a centre of revolt. Opposition sources said at least 20 people had been killed in army attacks there in the last two days.
It is impossible to verify reports from Syria because authorities have denied access to independent journalists.
The British-based Syrian Observatory for Human Rights (SOHR) reported heavy fighting in al-Qusair, a town which lies close to the Lebanese border. Three residents died in the fighting and four soldiers were killed when rebels ambushed their checkpoint.
Syrian troops also attempted to storm the northern town of Sermeen on Thursday, killing two people and wounding dozens, the SOHR said, quoting its network of contacts within Syria.
"Syrian forces are still not able to get inside the town because of fighting, but they are shelling Sermeen and using heavy machine guns," said SOHR head Rami Abdelrahman.
Fighting also erupted in southern Deraa, where several soldiers died in an ambush, he said, while Assad's forces conducted raids in the eastern province of Deir al-Zor and coastal Latakia province to try to snuff out rebel fighters.
NO PLAN YET
The Security Council's statement was supported by Russia and China, which had both vetoed previous Council resolutions, marking a rare moment of global unity over the crisis. It backed a peace drive by U.N.-Arab League envoy Kofi Annan and warned of "further steps" if Syria failed to respond.
Annan's six-point peace proposal calls for a ceasefire, political dialogue between the government and opposition, and full access for aid agencies. It also says the army should stop using heavy weapons in populated areas and pull troops back.
But Turkish Foreign Minister Ahmet Davutoglu said the statement did not yet signal that foreign powers had found a unified position to create a plan of action.
"Of course that is not everything, that we simply have a common message. We also need to work out a common action plan," he told reporters during a visit to Vienna on Thursday. "We have in this regard not been able to see a common position."
The U.N. statement, which lacks the legal force of a resolution, talks of the need for political transition in Syria, but it does not demand that Assad to step down - something both the rebels and the Arab League have called for.
"In clear and unmistakable terms, the Security Council called for an immediate end to all violence and human rights violations," U.N. chief Ban said in Malaysia.
Syria's official news agency appeared to play down the Council statement, saying it contained "no warnings or signals".
At least 8,000 people have died in the revolt, according to U.N. figures issued a week ago, and diplomats have warned that without a swift resolution, the conflict could spread and degrade already tense sectarian relations across the region.
Underlining the dangers, several stray Syrian shells fell in the Lebanese border village of al-Qaa and nearby fields late Wednesday, wounding one person, residents said.
"More than five shells landed in the fields and in the village," a farmer in al-Qaa told Reuters. Another resident said one shell had detonated next to the main school.
Human Rights Watch accused Syrian forces of committing "serious abuses" in Qusair, a town near the Lebanese border.
"Following their bloody siege of Homs, the Assad forces are applying their same brutal methods in Qusair," said Sarah Leah Whitson, the New York-based group's Middle East director.
"Having seen the devastation inflicted on Homs, the Russian government should stop arms sales to the Syrian government or risk becoming further implicated in human rights violations."
Russia has defended its long-standing military ties with Syria and has said it sees no reason to modify them.
Syrian Foreign Ministry spokesman Jihad Makdesi said this week that 3,000 members of the security forces had died in the uprising, which Damascus blames on terrorist gangs.
Earlier this week, Human Rights Watch accused opposition forces of committing rights abuses on state troops and their militia allies, including torture and summary execution.
RUSSIA HEDGING BETS
The European Union is set to impose further sanctions on Assad's inner circle on Friday, including his wife Asma, who described herself as "the real dictator" in an email published by Britain's Guardian newspaper last week.
"Tomorrow we will decide on new sanctions, not only against the Assad regime but also against the people around him," German Foreign Minister Guido Westerwelle told Deutschlandfunk radio.
He added that the unanimous U.N. statement was an important contribution to solving the crisis in Syria.
"Assad cannot depend on the protective hand of Russia in the violence against his own people and that could accelerate the process of erosion of the regime," Westerwelle said.
Although Russia has stuck to its demand that Assad must not be deposed by foreign powers, it has taken a sterner line this week, accusing the Syrian leadership of mishandling the crisis.
Analysts say this shows Russia is hedging its bets about Assad's fate and is positioning itself for his possible fall.
"Russia will not be focused on keeping Assad in power for the sake of keeping Assad in power," said Dmitry Trenin, director of the Carnegie Moscow Centre think tank.