Iranian President Mahmud Ahmadinejad on Tuesday commented for the first time on the violent opposition protests that have been held in the Islamic republic since Sunday, calling them "a nauseating display" initiated by foreigners. "The Iranian nation has seen many displays of this kind, the Zionists and Americans instructed it," the Iranian IRNA news agency quoted Ahmadinejad as saying. Iran's worst internal violence in the three decades has grown increasingly violent and bitter in the wake of clashes Sunday that left at least eight people dead. Security forces also arrested a relative of opposition leader Mir Hossein Mousavi on Tuesday, while government supporters held rallies in at least three cities. Earlier Tuesday, Iran accused the US and Britain of fomenting the violence, threatening to "slap" Britain in the face as it summoned the British ambassador to an urgent meeting. At a news conference, Foreign Ministry spokesman Ramin Mehmanparast said the deadly clashes in Teheran were the work of a tiny minority, and he accused outside countries, including the US and Britain, of "miscalculating" by siding with the protesters. "Some Western countries are supporting this sort of activities. This is intervention in our internal affairs. We strongly condemn it," he said. "In this regard, the British ambassador will be summoned today." He gave no further details, but Foreign Minister Manouchehr Mottaki threatened unspecified retaliation against Britain. "If this country does not stop its prattling, it will receive a slap in its face," he said during a news conference with his Somali counterpart. The quote was posted on the Web site of state TV. Also Tuesday, the son of leading opposition figure Mahdi Karroubi told The Associated Press by telephone that guards assigned to his father by Iranian police stopped on Monday providing security for him when he goes out, apparently under police orders. Police have for years provided leading opposition figures with security. Taghi Karroubi said the measure means his father cannot go outside safely, calling it a "quasi-house arrest." If Karroubi does go out unprotected he risks attack by hardline government supporters. His car was attacked on Saturday when he went out, and the assailants shattered his front windshield. Karroubi and opposition leader Mousavi were the two defeated reformist candidates in the disputed June 12 presidential election, which set off the worst unrest in Iran since the 1979 Islamic Revolution. The new arrests, along with tough criticism of the US and Britain, added to rising tensions with the West, which is threatening to impose tough new sanctions over Iran's suspect nuclear program and has criticized the violent crackdown on anti-government protesters. Sunday's clashes were the worst since the aftermath of June's disputed presidential election. There was no serious violence reported Tuesday, but opposition Web sites reported some 10 new arrests, including Dr. Noushin Ebadi. Ebadi, who won the 2003 Nobel Peace Prize for her human rights efforts in Iran, has stayed outside of Iran since a day before the June elections. She told The Associated Press in a phone interview from London that Iranian authorities were trying to punish her by arresting her sister. She said she called her sister Monday, and that she was being punished because of the conversation. "She was warned not to contact me," she said. "She is detained for the sake of me. She was neither politically active nor had a role in any rally."