Brent Pelkey, an American tourist who witnessed the stabbing, said the attack came out of nowhere on what appeared to be a normal day.

"I look ahead and I see a guy in a black suit running toward a group of tourists and he doesn't look like he has the best of intentions," Pelkey said. "Next thing I see is some tourists running around, some screaming, and the next thing I see is a few on the ground."

He approached the scene and saw a woman bleeding "profusely" from the side of her body. He said he saw three other people bleeding and on the ground "and obviously in some pretty serious pain" and then another person who looked like a park worker or guide also down.

Mexico's foreign minister, Marcelo Ebrard, said the attack occurred during a guided tour and confirmed that one person was seriously wounded and said a second was in surgery. "The Jordanian government has supported us throughout this," he tweeted.

Swiss authorities did not immediately comment.

Amateur video showed a bloody scene next to the Jerash archaeological site, an ancient city whose ruins include a Roman amphitheatre and a columned road.

In one video, a woman can be heard screaming in Spanish. "It's a dagger, it's a dagger, there is a knife. Please, help him now!"

One woman is seen lying on the ground, with much blood around her, as someone presses a towel to her back. Another man sits nearby with an apparent leg wound.

There were no immediate details on the identity of the attacker or his motives. But residents of the Jerash refugee camp, which is inhabited by Palestinians whose families left the Gaza Strip during the 1967 Mideast war, denounced the attack.

"We condemn the terrorist attack that was carried out by a coward in Jerash," they said in a signed letter quoted on a government newspaper's website.

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Jordan's economy relies heavily on tourism, and Islamic militant groups and other attackers have in the past targeted tourist sites to embarrass the government or harm the valuable industry. The Jordanian tourism sector has enjoyed a strong rebound over the past two years.

In 2005, triple hotel attacks killed at least 23 people, while the following year a British tourist was killed when a gunman opened fire at Roman ruins in Amman.

More recently, a 2016 attack by the Islamic State group killed 14 people, including a Canadian tourist.

AP