JERUSALEM: A senior Israeli official said Wednesday that it is "apparently clear" that chemical weapons were recently used in Syria, and that the alleged attack will be a main topic of conversation with visiting President Barack Obama.

The statement by Yuval Steinitz, the newly appointed minister of intelligence and strategic affairs, conflicts with U.S. assessments that there is no evidence behind accusations traded the day before between Syrian rebels and the Bashar Assad regime of a chemical weapons attack in a village in the north of the country.

Steinitz, who was speaking to Army Radio, did not say how he came to the conclusion that the weapons were used. He would not comment on whether it was Assad forces or the rebels that used them, saying it was not important.

A senior defense official told the Associated Press that he concurred chemical weapons had been used, basing that on intelligence reports. He would not elaborate. He spoke anonymously because he is not allowed to speak to the media.

Israel has repeatedly expressed concern that Syria's chemical arsenal could fall into the hands of anti-Israel militants like Lebanon's Hezbollah, an Assad ally, or an al-Qaida-linked group fighting with the rebels.

Steinitz said that after Iran's nuclear program, the fate of Syria's chemical weapons is the second most urgent issue that will be discussed with Obama during his 48 hour visit that begins Wednesday afternoon.

"It is apparently clear that chemical weapons were used," Steinitz said. "The fact they apparently used chemical weapons against civilians needs to worry us and shows the urgency of taking care of the issue," he said.

Syrian rebels and Assad's government blamed each other Tuesday for a chemical attack on a northern village. There have been many reports and rumors of such weapons being used throughout the war but no attack has yet been confirmed. The U.S. said there was no evidence chemical weapons were used.

The use of such weapons would be a nightmare scenario in the 2-year-old conflict that has killed an estimated 70,000 people, and the competing claims showed willingness by both sides to go to new levels to seek support from world powers.

President Barack Obama has declared the use, deployment or transfer of the weapons would be a "red line" for possible military intervention by the U.S. in the Syrian conflict.

The Syrian state-run SANA news agency said "a missile containing a chemical substance" was fired at the village of Khan al-Assal in Aleppo province by "terrorists" - the term it uses for rebels. Syria's Deputy Foreign Minister Faysal Mekdad said 31 people were killed.

SANA added that more than 100 others were wounded, some of them critically, and it published pictures showing casualties, including children, on stretchers in what appears to be a hospital ward. None showed signs of physical injuries. The rebels quickly denied using chemical weapons and accused regime forces of doing so.

The Aleppo Media Center, affiliated with the rebels, said there were cases of "suffocation and poison" among civilians in Khan al-Assal after a missile was fired at the area. It said in a statement the cases were "most likely" caused by regime forces' use of "poisonous gases."

Israel says it is trying to stay out of Syria's civil war, although it has strongly signaled that it was responsible for an airstrike in January and suggested it was targeting a Hezbollah convoy carrying anti-aircraft missiles to Lebanon.

It is concerned however about violence spilling into northern Israel.

The military says four wounded Syrians approached the Israel-Syria frontier on Wednesday and received medical treatment from Israeli troops. It said two of the Syrians are receiving medical aid adjacent to the border fence, while the two others were evacuated to Israeli hospitals following the severity of their injuries.