Bahrain's King Hamad bin Isa Al Khalifa on Thursday approved changes to the country's constitution aimed at ending a nearly 15-months-old popular revolt in the Gulf state.

The amendments include giving parliament more powers to question and remove government ministers.

During a ceremony in Manama, King Hamad said that “the door of dialogue is open and national accord is the goal of all dialogue.” He expressed hope that all forces and groups will assess their actions and join the process of progress and reforms in this important stage.

But the main opposition party, al-Wefaq, denounced the amendments as inadequate, saying they fall short of demands of protesters from the country's Shi'ite majority, which demands a greater political voice in Bahrain's affairs.

Shi'ites account for about 70 percent of Bahrain's population of just over 500,000 people, but claim they face widespread discrimination and lack opportunities granted to the Sunni minority. Some want Sunni rulers to give up their monopoly on power, while others want the ruling al Khalifa family to be ousted completely.

Bahrain's Sunni rulers have offered a dialogue with the opposition on political reforms. But many Shi'ites say they will continue protesting in the streets until the government accepts their demands.