Post-Gaddafi planning begins in US, EU and NATO; UK fears post-Saddam type anarchy could break out in Tripoli; Hamas welcomes rebel progress.

International leaders reacted late Sunday and Monday to developments in Libya that saw rebels enter and take control of most of the capital, with some calling on Libyan leader Muammar Gaddafi to step down voluntarily and others demanding he be tried in the International Criminal Court in the Hague.

US President Barack Obama said on Sunday that Gaddafi's rule was showing signs of collapse and called on the Libyan leader to relinquish power to avoid further casualties.