NEW YORK (AP) - Families of victims of the Sept. 11, 2001, terrorism attacks and a 1983 bombing of U.S. Marines in Lebanon are seeking to hold Iran accountable in separate legal actions.

A lawsuit filed Monday in U.S. District Court in Manhattan seeks to enforce a $2.6 billion judgment against the Islamic Republic of Iran awarded by a federal court in Washington, D.C. That September 2007 award stemmed from claims that Iran was involved in an October 1983 bombing that killed 241 servicemen at a U.S. Marines facility in Beirut.

The lawsuit seeks to obtain ownership of a Fifth Avenue office tower that the U.S. government has alleged is partially owned by a shell company fronting for a secret interest held by Bank Melli, the state-owned bank of Iran. The U.S. government has already begun forfeiture proceedings to gain control of the property.

Meanwhile, lawyers for families of victims of the 2001 attacks seek in a separate lawsuit to force the government of Iran to pay damages for supporting terrorism. They filed papers Monday saying they will attempt to use recent laws that make it more difficult for states accused of supporting terrorism to claim sovereign immunity.

No lawyers have represented Iran in the actions.