BEIJING — Tibetan protests against Chinese rule intensified around the opening of a pivotal Communist Party congress as three teenage monks and two other Tibetans set themselves on fire over two days, activists reported Thursday.

Four of the self-immolations took place Wednesday and were followed by a fifth involving a nomad in western Qinghai on Thursday. Since March 2011, dozens of ethnic Tibetans have self-immolated in ethnically Tibetan areas to protest what activists say is China’s heavy-handed rule over the region. Such protests have become more frequent in recent weeks, apparently aimed at the party’s weeklong conference to unveil the country’s new leadership that opened Thursday.