Rioting broke out here and in three other cities yesterday, and a sniper killed a part-time soldier. Roman Catholic activist Bernadette Develin McAliskey said, "The wrath of the people will be vented" if hunger-striking IRA terrorist Bobby Sands dies in Maze Prison.

Former U.S. attorney general Ramsey Clark said British Prime Minister Margaret Thatcher has "made a grievous mistake" by repeated refusals to treat jailed Irish Republican Army activists as political prisoners rather than criminals. Sand, recently elected to Parliament from a Catholic district, was in the 54th day of a hunger strike to win political prisoner status and is reported near death.

Clark and McAliskey spoke at a news conference that also was attended by the Rev. Daniel Berrigan. Clark and Berrigan traveled to Belfast hoping to see Sands, but Britain denied the request, saying "it would serve no useful purpose."

The rioting erupted in West Belfast and the Falls Road district of the capital, Dungannon, Strabane and Lurgan, pitting Catholic youths hurling stones and firebombs against police and troops.

In Washington, 21 members of Congress asked President Reagan in a telegram to urge Thatcher to seek "a humanitarian resolution" or risk more violence in Ulster.