Israeli soldier assaults foreign protester. WARNING: This video contains graphic images Source: YouTube/LIKMA38 YouTube/LIKMA38

Denmark has demanded an explanation from the Israeli government for video footage showing a senior Israeli army officer striking a Danish activist in the face with an M16 rifle, an act which has been sharply criticised by the Israeli prime minister, president and chief of staff.

In the video, Lt Col Shalom Eisner, deputy commander of the Jordan Valley territorial brigade, is clearly seen slamming his rifle into the face of Andreas Ias. There was no obvious reason for the assault in the clip, which was broadcast on Israeli television and posted on YouTube. The soldier was suspended by the Israeli Defence Forces (IDF) pending an investigation.

The video emerged on the same day as Israel launched a security operation to prevent hundreds of pro-Palestinian activists entering the country en route to the West Bank, claiming they were provocateurs and were planning acts of violence. The assault on the Danish man and the operation to block the entry of Palestinian sympathisers have led to questions about whether Israel's response to activists is excessively heavy-handed and will damage its image.

The Danish ambassador to Israel, Liselotte Plesner, asked for detailed information about the assault on the activist. A statement from Denmark's foreign foreign minister, Villy Sovndal, said: "We are not aware of all the circumstances surrounding the incident. The Danish ambassador has asked the Israeli authorities for an immediate explanation."

Ias, 20, was part of a large group of European pro-Palestinian activists cycling near Jericho on Saturday when, according to Palestinian media reports, the IDF stopped the participants. Israel said the protesters were attempting to block the road. In the ensuing scuffle, some activists were injured and taken to hospital, and others were arrested.

Prime Minister Binyamin Netanyahu condemned the soldier's actions, saying: "Such conduct is not characteristic of the soldiers and commanders of the Israeli military, and has no place in the army or the state of Israel."

President Shimon Peres said he was shocked, and Benny Gantz, the Israeli chief of staff, described it as "a severe incident, which contravenes the IDF's values", saying it would be investigated thoroughly. The IDF routinely claims it is the most moral army in the world.

However, friends of the suspended IDF officer claimed that the demonstrator had fractured bones in the soldier's hand before the incident. The soldiers had acted with restraint, tried to calmly disperse the activists blocking the road, and only retaliated when they were attacked, they added.

Ias said the event had been non-violent, and there had been no verbal exchange or contact between him and the officer before he was hit in the face. He was taken to hospital where he had stitches to his lips.

"It's surprising to me that there's this big reaction," he said on Israeli television on Monday night, saying that he had seen similar incidents "all the time" in the West Bank.

Suggestions that Israel had over-reacted to the impending arrival of hundreds of pro-Palestinian activists at Ben Gurion airport on Sunday were fuelled by the admission by its foreign ministry that many people named on "no-fly lists" were not known activists.

The Israeli authorities demanded that airlines bar people on the list from boarding planes or face possible sanctions. But there was no evidence or information to suggest that around 470 of the 1,200 names on the list had any connection to pro-Palestinian groups or history of activism. "We don't know why they were there," a spokesman for the Israeli foreign ministry told the Associated Press.

Most of those who were planning to attend a week of cultural and educational events in the West Bank were barred from travel, and around 80 were detained at Ben Gurion airport. Only three out of an estimated 1,500 intended participants reached Bethlehem.

The video of Saturday's incident was uploaded to YouTube by the International Solidarity Movement (ISM), whose members take part in protests and events in the West Bank and Gaza. In 2003, ISM activist Rachel Corrie was killed trying to block an Israeli bulldozer from demolishing a house in Gaza, and the following year ISM volunteer Tom Hurndall was shot in the head by an IDF sniper, also in Gaza. He died after nine months in a coma.