(KUNA) -- Some 50 Iraqi terrorists were killed and 21 others were arrested in clashes between Iraqi and multinational forces in Heifa Street in Karkh in Baghdad on Tuesday, an Iraqi defence ministry spokesman said. Of the insurgents arrested in the ongoing military operation, there were Arab nationals, Spokesman Mohammed Al-Askari told Kuwait News Agency (KUNA). But, he failed to reveal where those Arab nationals are from.Earlier on Tuesday, the US army said its troops and Iraqi forces launched a crackdown operation on the area where the clashes took place in order to regain security control over northern Heifa Street. Iraqi security forces said 30 militants were killed and eight others, including Sudanese and Syrians, were arrested in clashes at the same area last Sunday after corpses of people slain by insurgents were found there. KUNA correspondent in Baghdad said Tuesday he saw several US helicopters raiding several sites in Heifa Street, which has been closed by security forces since early morning.