(Corrects paragraph 2 to make clear that Hamas has **t been declared a terrorist group in Egypt) By Nidal al-Mughrabi GAZA, March 23 (Reuters) - Tens of thousands of Palestinians rallied in Gaza on Sunday to show support for their Islamist Hamas government, which has long been at loggerheads with Israel but is **w shunned by Egypt as well. The military-backed government that toppled the Muslim Brotherhood, Hamas's ideological kin, in Cairo last year deems the Palestinian faction a security threat. An Egyptian court this month banned Hamas activities in the country, and Cairo has clamped down on smuggling tunnels across the Sinai-Gaza border. Hamas tried in vain to mollify Egypt by insisting that its hostility was directed exclusively at Israel, but is **w turning up the rhetoric.