LONDON (AFP) - Britain summoned Irans ambassador Friday as the international powers made new warnings to the Tehran leadership over the handling of election result demonstrations. A EU summit called on Iran not to use violence against peaceful demonstrators. The UN High Commissioner for Human Rights expressed concern over the number of arrests in a clampdown on the protests. Irans ambassador to London was summoned to the Foreign Office, a British spokesman said, in a new sign of the diplomatic strains caused by the disputed election which Iranian authorities say returned Mahmoud Ahmadinejad to a second term as president. The Foreign Office spokesman did not say why the ambassador, Rasoul Movahedian, was summoned, but the action came after Irans supreme leader Ayatollah Ali Khamenei singled out Britain for criticism in a speech. British Prime Minister Gordon Brown said his government would carry on criticising Iran and that the whole world is watching the events in Tehran. Brown and other EU leaders discussed the clampdown at a Brussels summit which called on the Iranian govt to allow peaceful protests. The leaders urged the Iranian authorities to ensure that all Iranians are granted the right to assemble and to express themselves peacefully, said a summit statement. The authorities should refrain from the use of force against peaceful demonstrations, it added. French President Nicolas Sarkozy urged Iran not to go beyond the point of no return. UN Human Rights Commissioner Navi Pillay expressed concern over the use of excessive force to quell the Tehran protests in which at least seven people have been killed. A spokesman for the UN rights chief, Rupert Colville, said indirect information suggested that hundreds of people have been arrested. Two leading US lawmakers on Friday put forward a resolution condemning the crackdown against Iranian demonstrators following disputed presidential elections. The resolution expresses its support for all Iranian citizens who embrace the values of freedom, human rights, civil liberties, and rule of law, according to the text from Democrat Howard Berman, Chairman of the House Foreign Affairs committee, and Republican Mike Pence. It also condemns the ongoing violence against demonstrators by the govt of Iran and pro-govt militias, as well as the ongoing government suppression of independent electronic communication through interference with the Internet and cellphones.