President Michel Suleiman on Thursday expressed "grave concern" over the use of chemical weapons in Syria and condemned the firing of rockets from Lebanon at Israel as a "violation of Resolution 1701 and Lebanese sovereignty."

The president said that if confirmed the attacks would totally be in violation of “human values and principles.”

Israeli Prime Minister Benjamin Netanyahu warned on Thursday of retaliation after a volley of rockets were fired from southern Lebanon at the Jewish state, causing no casualties or damage.

"Anyone who harms us, or tries to harm us, should know -- we will strike them," he said in a televised address.

Unknown militants fired four rockets from the southern region of Tyre towards northern Israel on Thursday.

“Four rockets were fired from an area between Hawsh and the al-Rashidiyeh (Palestinian refugee) camp towards the Occupied Territories (northern Israel),” Lebanon's National News Agency reported.

A senior Palestinian official accused Israel on Thursday of preventing the United States from taking part in peace talks, two days after a new round of meetings.

"The American side has not participated in any meetings until now between Israel (and the Palestinians)," Palestine Liberation Organization secretary general Yasser Abed Rabbo told Voice of Palestine radio.

Russia received the chief Palestinian negotiator with Israel on Thursday, urging the two sides to strengthen trust to build stability in the recently resumed Middle East peace negotiations.

"We understand that you are only at the very start. We want the resumed talks to assume stability," news agencies quoted Russian Foreign Minister Sergei Lavrov as telling Saeb Erakat at the start of their meeting.

Two Iranian men were sentenced to between 15 years and life Thursday for their parts in a botched bomb plot last year in Bangkok that ended with one of them having his legs blown off.

The pair, who had denied the charges, were among five Iranians suspected of involvement in blasts that Israel has linked to a 2012 spate of attacks on its diplomats across the world.

Contradicting reports emerged on Thursday on whether Hamas is cooperating with the Lebanese army intelligence on handing over two witnesses in the May rocket attack that targeted Hizbullah controlled neighborhood of Shiyah, in Beirut's southern suburbs,

Hamas previously confirmed that Fadi Taha, the brother of the suspect Ahmed Mahmoud Taha, and his cousin were handed over to the intelligence bureau as witnesses.

Israeli Defense Minister Moshe Yaalon said on Wednesday that the Syrian government had used chemical weapons, backing opposition claims of multiple deadly strikes around Damascus.

"In Syria, the regime has used chemical weapons and it's not the first time," Yaalon told Israeli defense correspondents.

The Palestinians threatened Wednesday to sue Israel through international bodies if it continues expanding settlements in the occupied territories, warning it was an issue that could torpedo fledgling peace talks.

"These are not just dots on a map," PLO executive committee member Hanan Ashrawi said of more than 2,000 new settler homes which were approved for construction ahead of a resumption of peace negotiations late last month.

An Israeli force on Wednesday deployed and staged a military parade near al-Wazzani border region, provoking the national army to increase its security alert.

"Around 22 troops deployed on the outskirts of the eastern Wazzani region near the barbed wire,” the NNA detailed.