A dissident leader recently released from prison died under mysterious circumstances during a crackdown on the Azerbaijan opposition involving 29 arrests in two days, opposition parties said Thursday. Ehtiram Jalilov, 35, deputy head of Azerbaijan's National Democratic Party, became the second opposition activist to die in unexplained circumstances this year, an allied opposition party, Musavat (Equality), said. Jalilov was sipping tea with a colleague on Wednesday when he slumped dead at the table, according to Qabil Huseynli, deputy head of Musavat, one of the former Soviet republic's best known opposition parties. In February, a 21-year-old Musavat activist died under similar circumstances. Huseynli called for the creation of an international panel of doctors to investigate the deaths, saying that medics the party has consulted believe "the deaths could have been caused by an unknown powder used by the special services against undesirables." Twenty nine opposition activists, 18 of them Musavat party members, have been arrested over the past two days for minor infractions such as disturbing the peace and resisting arrest ahead of an anti-government rally planned for Saturday, Huseynli said. "We think this has to do with the protest. The authorities are concerned that it will be huge and are arresting those people they think are responsible for its organization," Huseynli said.