Activists said at least 15 civilians and seven soldiers were killed on Wednesday in the latest violence sweeping protest-hit Syria, including deadly clashes near the Lebanese border.

Syria's leading opposition grouping, the Syrian National Council, meanwhile, threatened to seek foreign intervention to stop the regime's deadly crackdown against pro-democracy protesters.

A Syrian rights group called on Tuesday for President Bashar al-Assad to be tried for "crimes against humanity" as troops reportedly mounted the fiercest raids in the Damascus region of their seven-month crackdown on dissent.

Activists also reported that security forces shot dead three people in the southern province of Daraa, cradle of the anti-regime protests that erupted in mid-March, and a fourth in the town of Qusayr on the Lebanese border.

Crowds of Palestinians, many of them overwhelmed and in tears, welcomed home hundreds of freed detainees in the West Bank and Gaza on Tuesday, under a landmark prisoner exchange deal with Israel.

The 477 prisoners, the first of two groups of Palestinian detainees being exchanged for captured Israeli soldier Gilad Shalit, arrived in the West Bank, east Jerusalem and Gaza late morning Tuesday.

French President Nicolas Sarkozy on Tuesday hailed the release of dual-nationality Israeli soldier Gilad Shalit as "a huge relief for France", voicing hope that stalled peace talks could now restart.

Sarkozy said that Shalit, captured by Gaza-based Palestinian militants in 2006 and released on Tuesday in exchange for Israel freeing hundreds of Palestinian prisoners, would "soon" travel to France.

Turkey claims "very significant contributions" for the release of Israeli soldier Gilad Shalit, Anatolia news agency quoted deputy prime minister Bulent Arinc as saying on Tuesday.

"In this exchange ... and in protecting the life of Shalit until today, Turkey made very significant contributions," Arinc said without elaborating.

Turkey was shelling northern Iraq's autonomous Kurdistan region on Tuesday, a Kurdish rebel spokesman said, in the first report of Turkish bombardment in the area in more than two weeks.

The shelling began Monday night "against Khowakirk and Zab in northeast Dohuk" province, said Dozdar Hammo, a spokesman for the Kurdistan Workers' Party (PKK), which operates out of bases in Kurdistan.

U.S. Secretary of State Hillary Clinton flew in to Tripoli on Tuesday as Libya's new rulers try to crush the last pockets of resistance by fighters loyal to ousted leader Moammar Gadhafi.

The first U.S. cabinet official to visit Libya since 2008 when Washington wanted to forge a new relationship with Gadhafi, Clinton is seeking to bolster ties with the new rulers and promote Libya's transition to democracy.

Israeli soldier Gilad Shalit, who was freed on Tuesday after five years in detention by Palestinian militants, said he hoped the prisoner swap in which he was liberated would lead to peace between both sides.

"I hope this deal helps achieve peace between both sides, Israel and the Palestinians," he told Egyptian television in his first interview since his release.

Turkish Foreign Minister Ahmet Davutoglu has met with leaders of Syria's opposition movement urging unity in pursuit of a peaceful transition in the country, a Turkish diplomat said Tuesday.

"The minister met with representatives of the Syrian opposition, for the first time, in Ankara on Monday," the diplomat told Agence France Presse on condition of anonymity.

Yemen's Nobel Peace Prize winner Tawakkul Karman said the U.N. must act "immediately and decisively" to halt a deadly government crackdown on protesters calling for President Ali Abdullah Saleh to resign.

Karman urged the United Nations "to take immediate and decisive action to stop the massacres and hold the perpetrators accountable," in a letter to U.N. chief Ban Ki-moon, a copy of which she showed to Agence France Presse late Monday during a visit to Doha.