A Kuwaiti court on Thursday freed three Twitter users on bail after detaining them for nine days for allegedly insulting the ruler of the oil-rich Gulf state, a rights activist said.

A fourth tweeter however remained in detention as his case will be heard by a court on Sunday, the director of the Kuwait Society for Human Rights, Mohammad al-Humaidi, said on his Twitter account.

A Palestinian woman in her late 30s was arrested on Thursday after trying to stab an Israeli border guard at the entrance of an east Jerusalem police station, police said.

It was not immediately clear what prompted the woman to attack the border guard, who suffered only scratches, a statement said, indicating that an investigation was under way.

The Kuwaiti government on Thursday launched a media campaign to convince voters to cast their ballot in the December 1 poll in a bid to counter opposition calls for a boycott over a disputed law.

The campaign comes a day after Emir Sheikh Sabah al-Ahmed al-Sabah urged the public to be "positive" and cast their votes to elect the best candidates.

Russia on Thursday warned Turkey against deploying surface-to-air Patriot missiles to protect its troubled border with Syria, saying it should instead use its influence to help broker peace in the war-torn country.

"The militarization of the Syrian-Turkish border is of course a worrying sign," foreign ministry spokesman Alexander Lukashevich told a briefing.

Sudan on Thursday said it arrested 13 people including the former head of the country's powerful intelligence service for an alleged plot to sabotage national security.

A witness saw armored vehicles moving in the streets of the capital before daybreak, as state-linked media first reported that the "plot" had been averted.

Life in Gaza began returning to normal on Thursday with a public holiday to mark a ceasefire that ended a violent eight-day confrontation with the Israeli military.

After days and nights cooped up at home, their buildings rocked by an unrelenting Israeli bombing campaign and the sound of outgoing Palestinian rocket fire, residents were eager to reclaim their hometowns and their lives.

At least 40,000 people have been killed in violence across Syria since the outbreak of an anti-regime revolt in March last year, the Syrian Observatory for Human Rights said on Thursday.

"At least 28,026 civilians, 1,379 defectors, 10,150 soldiers and 574 unidentified people have been killed in Syria in the past 20 months," said Observatory director Rami Abdel Rahman.

Israeli troops arrested 55 Palestinian "terror operatives" across the West Bank overnight, hours after a truce came into effect in the Gaza Strip, the army said on Thursday.

"A total of 55 terror operatives, who are affiliated with different terror groups have been detained. Among those arrested were a number of senior level operatives," a statement said, with public radio saying it included members of Hamas and Islamic Jihad.

Rebel fighters seized the town of Mayadeen in eastern Syria on Thursday, a monitoring group said, adding that a large area on the Syrian-Iraqi border is now under control of insurgents.

"The area east of the city of Deir Ezzor, on the Iraqi border, is now the largest area in the whole country that is out of army control," said Syrian Observatory for Human Rights director Rami Abdel Rahman.

Defense Minister Ehud Barak warned on Thursday that Israel may resume its attacks on Gaza at any time if a truce that ended a week of bloodshed fails to hold.

The ceasefire "can last nine days, nine weeks or more, but if it does not hold we will know what to do, and then of course we shall consider the possibility of resuming our (military) activity in case of shooting or provocation," he told public radio.