The Syrian regime has begun using missiles and barrel bombs against opposition rebels in the past week or so, a top U.S. official said Wednesday, denouncing the increasing use of "vicious weapons."

Amid reports that Scud missiles have been fired, State Department spokeswoman Victoria Nuland said she "was not in a position to confirm types of missiles, simply to say that we're seeing missiles employed now."

An Omani appeals court upheld on Wednesday jail sentences ranging from six months to one year against 23 activists convicted for defaming the sultan and taking part in pro-reform protests last year.

The court in Muscat confirmed a one-year jail term against 11, including writers and bloggers and a young woman, accused of insulting the sultan and cyber crimes, ONA state news agency said.

Israeli border guards shot dead on Wednesday a Palestinian teenager armed with a pistol in the West Bank city of Hebron, sparking stone-throwing attacks on troops in the area, police and witnesses said.

"A Palestinian brandished a pistol as he approached a post of border guards, who opened fire and killed him," a police spokeswoman said.

The head of the Syrian National Coalition has been invited for talks in Washington following U.S. recognition of the opposition bloc as the legitimate representative of the Syrian people, a senior U.S. envoy said on Wednesday.

"We have extended an invitation to (Ahmed) Moaz al-Khatib and the Coalition leadership to visit Washington at the earliest opportunity," Deputy Secretary of State William Burns said in Morocco, where he was attending a meeting of the Friends of Syria group.

Unknown attackers fired at a convoy transporting United Nations personnel east of the Libyan capital on Wednesday, a U.N. spokeswoman told Agence France Presse, adding that no one was hurt.

"Yes, indeed there has been an incident. A U.N. convoy was shot at. There were no injuries," said Radia Achouri, confirming reports that the attack took place in Khoms, 100 kilometers (60 miles) east of Tripoli.

Explosions outside the Syrian interior ministry, including a car bomb, killed seven people and wounded 50 others on Wednesday, a security official said.

Interior Minister Mohammad al-Shaar and other top ranking officials escaped unharmed, state television reported.

Libya on Wednesday reiterated its call for the extradition of slain Libyan strongman Moammar Gadhafi's son Saadi from Niger, which has granted him asylum since September 2011 on "humanitarian" grounds.

"The Libyan party has noted the threat posed by the presence in Niger of members of the former Libyan regime," said a government statement issued after a visit to Niamey by Libyan Prime Minister Ali Zeidan.

An Egyptian journalist who was hit in the head by a rubber bullet while covering bloody clashes in Cairo last week has died in hospital from his injuries, the state MENA news agency reported on Wednesday.

El-Husseini Abu Deif, a reporter for the al-Fajr independent news weekly, had been in a coma with a fractured skull and severe brain injury, it said.

Tunisia's main labor union, the UGTT, said on Wednesday it had called off a nationwide general strike convened to protest what it said had been an attack on its offices by allies of the ruling Ennahda party.

The UGTT "administrative commission decided to cancel the general strike," which had been set for Thursday, a union statement said, explaining that the decision was taken after a deal with the government to head off the work stoppage.

Egypt's crisis showed no sign of easing on Wednesday as the army delayed unity talks meant to ease political divisions and the opposition set near-impossible demands for not boycotting a constitutional referendum.

Voting on the controversial Islamist-backed draft charter is due to start on Saturday, with a second round scheduled for a week later following a last-minute decision by the electoral commission to spread polling over two days.