JERUSALEM, Jan 23 (Reuters) - Israeli police on Monday two senior Hamas members at an International Committee of the Red Cross building in East Jerusalem where they had taken shelter for some 18 months, Red Cross and Israeli officials said.

Palestinian lawmaker Mohammed Totah and Khaled Abu Arafah, a former cabinet minister, face possible expulsion from the city when they appear before an Israeli judge this week, Micky Rosenfeld, an Israeli police spokesman said.

The ICRC confirmed the arrests and said that as East Jerusalem was an occupied territory under international law, Israel was not allowed to forcibly transfer Palestinians.

Israel had revoked Totah and Arafah's Jerusalem residency permits in July 2010, a step it has also taken against other Hamas members.

Two Hamas activists were arrested at the Red Cross building. They were hiding in the building for a year and a half after their ID cards had been revoked on suspicions of being active in terrorist activity, Rosenfeld said.

Israel, along with the United States and the European Union, considers the Islamist Hamas movement a terrorist group. Hamas condemned the arrests as kidnapping by the Zionist enemy.

Israel captured East Jerusalem in 1967 and annexed it as part of its capital in a move never recognised internationally. Palestinians want East Jerusalem as capital of a state they seek to establish in the West Bank and Gaza Strip.

In response to Monday's arrests, a crowd of Palestinians smashed the gate of the Red Cross compound in Jerusalem, angry at what they charged was the organisation's failure to protect Totah and Abu Arafah.

Hamas said both men deserved immunity from arrest because they were public officials.

In Geneva, ICRC spokesman Hicham Hassan said: It will not be in accordance with international humanitarian law to deport the men as East Jerusalem is considered occupied land and its Palestinian residents protected by the Fourth Geneva Convention, which prohibits forcible transfers of people.

Palestinian officials said at least 26 Palestinian lawmakers were in Israeli detention.

Last week, the speaker of the Palestinian Legislative Council, Aziz Dweik, also of Hamas, was detained on suspicion of what the Israeli military termed involvement with terrorist groups.

(Additional reporting by Stephanie Nebehay in Geneva, Labib Nasir and Ari Rabinovitch in Jerusalem, writing by Sami Aboudi)