TEHRAN (Reuters) - Irans supreme leader called on the Opposition on Tuesday to distance itself from the Islamic Republics Western enemies, in a warning ahead of expected new anti-government protests next month. Tension has risen in Iran after eight people were killed in clashes between the security forces and Opposition supporters on Ashura that fell on December 27. It was the worst violence in the major oil producer since the aftermath of last years disputed presidential election and was followed by the arrests of scores of pro-reform figures in a fresh crackdown by the authorities. Despite intensifying pressure, Opposition backers are expected to take to the streets again on February 11, when Iran marks the 31st anniversary of the 1979 Islamic revolution. Supreme Leader Ayatollah Ali Khamenei, who has urged tougher action against the demonstrators, said Irans foes were seeking to harm its unity. Government officials have portrayed the huge Opposition protests that erupted after the June election as a foreign-backed bid to undermine the clerical leadership. All parties with different tendencies should clearly distance themselves from the enemies, particularly influential elites should avoid making ambiguous comments ... when arrogant powers and oppressors adopt anti-Islamic stances, he said. Referring to the state-sponsored rallies usually on the revolution anniversary, Khamenei said the enemies are worried about the huge presence of our nation on that day and that they could not undermine the Islamic revolution. But in a sign of continued Opposition defiance, reformist former president Mohammad Khatami accused the authorities of launching a new wave of pressures and he defended people still protesting over the outcome of the election. Khatamis comments, reported by the pro-reform Parlemannews website, are likely to anger ruling hardliners who have repeatedly issued stern warnings against any more such rallies. Unfortunately we are witnessing these days a new wave of pressures and a new round of arrests, said Khatami, who backed Opposition leader Mirhossein Mousavi in the presidential poll. He was speaking at a meeting of freed post-vote detainees. Khatami, who was president from 1997-2005, said those handling Irans affairs had done nothing but caused more problems, in hard-hitting criticism of Ahmadinejads government. The people have realised that many of the protesters were not ill-wishers and their protests were right, Khatami said. The major part of the protesters are committed to the Constitution and peaceful ways to voice their protests. An Iranian news agency, ILNA, on Tuesday cited police as saying that tip-offs from the public had helped the force to arrest 40 rioters who took part in last months protests. The arrests followed the detentions of hundreds of people on Ashura itself. On Monday, five people went on trial in a Tehran court on charges that could be punishable by death.