President Bashar Assad made a rare public appearance on Wednesday, vowing to defeat a "conspiracy" against Syria a day after he blamed foreign interests for stoking months of deadly violence.

"Without a doubt we will defeat the conspiracy, which is nearing its end and will also be the end for (the conspirators) and their plans," Assad told tens of thousands of cheering supporters in the capital's central Omayyad Square.

An Arab League observer in unrest-swept Syria said Wednesday he has quit the mission, accusing the regime of committing a series of war crimes against its people and of duping his colleagues.

"I withdrew from the Arab observers mission because I found myself serving the regime, and not part of an independent observer group," Anwar Malek told the Doha-based news channel Al-Jazeera.

Cypriot authorities released on Wednesday a cargo ship carrying tons of munitions after receiving confirmation the vessel would not proceed to Syria as originally scheduled.

The ship called into Limassol port for refueling on Tuesday following bad weather, said government spokesman Stefanos Stefanou.

Hundreds of Syrian and international activists will try to cross into Syria from Turkey and Jordan on Thursday in a bid to take humanitarian aid to the Syrian people, various sources said.

"Our aim is ... to deliver humanitarian aid to the families in the afflicted areas that suffer from daily brutal bombing and totally unacceptable living conditions," said a statement posted on the website of the group called "Freedom Convoy".

Three Palestinian cars were set alight overnight in a village in the northern West Bank, a local official and police said in what appeared to be the latest "price tag" attack.

The incident took place in Deir Istiya village, 15 kilometers southwest of Nablus and sandwiched between the Ariel settlement bloc and the Karnei Shomron bloc.

Unidentified gunmen killed a Yemeni intelligence official and wounded seven others in an attack on their mini-bus in the southern port city of Aden, security and medical officials said Wednesday.

The gunmen first stopped the vehicle travelling in Aden's Khor Maksar neighborhood in the city center before opening fire on the passengers, a police official told Agence France Presse on condition of anonymity.

Insurgents attacked an Iraqi police station near the Syrian border early Wednesday morning and killed three policemen, including a captain, security and medical officials said.

Police managed to kill one of the gunmen who carried out the 3:00 am (00:00 GMT) attack in the town of al-Qaim, in the mostly Sunni Anbar province west of Baghdad, and wounded another. A third shooter escaped.

The U.S. State Department's number two was to meet Wednesday with leaders of the Muslim Brotherhood's party after it claimed a crushing victory in landmark post-revolution parliamentary elections.

William Burns "will meet leaders of the Freedom and Justice Party at their headquarters in Cairo," FJP spokesman Ahmed Sobea told Agence France Presse.

Iran said Israel and the United States were behind a car-bomb assassination of one of its nuclear scientists in Tehran on Wednesday, calling it a "terrorist act" in the same vein as previous killings of other Iranian scientists.

"This terrorist act was carried out by agents of the Zionist regime (Israel) and by those who claim to be combatting terrorism (the United States) with the aim of stopping our scientists from serving" Iran, Vice President Mohammed Reza Rahimi told state television.

Four hundred people have been killed in Syria since Arab League monitors started a monitoring mission on December 26, and 40 people are being killed each day, a top U.N. official told the Security Council on Tuesday.

U.N. assistant secretary general B. Lynn Pascoe gave the new casualty figure in a closed meeting of the 15-member Council, according to envoys.