Syrian security forces and pro-regime militias have executed more than 100 civilians and rebel fighters in attacks on protest hubs since late 2011, Human Rights Watch said on Monday.

Many of the summary and extrajudicial executions were carried out last month, and at least 85 of those killed were residents who never took part in fighting, including women and children, said the New York-based watchdog.

Mortar rounds fired from the Syrian side of the border targeted a number of Lebanese towns in the vicinity of the al-Masharfeh area in the northern region of Wadi Khaled on Sunday evening, LBC television reported.

On Tuesday, Syrian troops staged a brief incursion into Lebanese territory amid fierce clashes with rebel forces, local official and residents said.

Belgium said Sunday that humanitarian intervention in Syria under the protection of military forces would be needed if the regime of Bashar Assad pursues the "path of barbarism".

"The regime has taken the path of barbarism and I trust President Bashar Assad less and less," said Belgian Foreign Minister Didier Reynders on TV5 television.

Clashes between government troops and army deserters raged on Sunday across Syria, where at least 84 people were killed and more than 200 arrested, activists and monitors said.

The weekend escalation in violence came ahead of a U.N. deadline of Tuesday for regime forces to cease fire, prompting harsh words from international envoy Kofi Annan who said the escalation was "unacceptable."

Jordan's King Abdullah II on Sunday reiterated calls to find a political solution in Syria and avoid more bloodshed in the neighboring country, where thousands have been killed in violence.

"Jordan believes in finding a solution to the Syrian crisis in line with Arab consensus and believes in supporting (peace envoy) Kofi Annan," a palace statement quoted the king as telling a U.S. congressional delegation.

Progressive Socialist Party leader MP Walid Jumblat on Sunday stressed that his support for the Syrian uprising does not imply a change in his domestic alliances, noting that his ministers will not resign from Premier Najib Miqati’s government.

“We stress the firm stances: we will stay in this government and we are with (Hizbullah’s) weapons in order to defend Lebanon in the face of Israel, but we reject the use of arms domestically,” Jumblat said during a meeting with his party’s cadres in the Mount Lebanon town of al-Khalwat.

Pope Benedict XVI called on Sunday for an end to bloodshed in Syria and a commitment to dialogue to end the violence there, as part of a wider appeal to give hope to the entire Middle East.

"May the risen Christ grant hope to the Middle East and enable all the ethnic, cultural and religious groups in that region to work together to advance the common good and respect for human rights," he said in his traditional "Urbi et Orbi" message to mark Easter Sunday.

The international mediator for Syria, Kofi Annan, said on Sunday he was shocked by the "unacceptable" surge in bloodshed there despite a U.N. deadline for a halt to all violence next week.

"I am shocked by recent reports of a surge in violence and atrocities in several towns and villages in Syria, resulting in alarming levels of casualties, refugees and displaced persons, in violation of assurances given to me," Annan said in a statement.

An online video shows Izzat Ibrahim al-Duri, Saddam Hussein's vice president and the highest-ranking member of his regime still on the run, in what appears to be his first video message since 2003.

The authenticity and date of the clip posted on YouTube on Saturday could not be verified.

Pope Benedict XVI will visit Lebanon from September 14 to 16, the Vatican announced on Sunday.

The trip will mark the second to the region for Benedict, who visited Jordan, Israel and the Palestinian Territories in 2009.