The annual hajj pilgrimage that brings some two million Muslims to the religion’s holiest site in Mecca has once again become the subject of political controversy as Muslims opposed to the government of Saudi Arabia are urging others to boycott the event.

Reuters described the boycott movement as “small” compared to the 1.8 million arriving in Mecca on Friday, and noted its organizers understand the difficulty of persuading Muslims not to undertake a journey they are supposed to make at least once in their lives, saying:

“#BoycottHajj is an important discussion for Muslims to have. It is about being critical and recognising the atrocities that the Saudi regime commits against fellow Muslims,” Mariam Parwaiz, a public health doctor in New Zealand, said on Twitter.

For Ella, attending haj now would be incompatible with Islam’s wider obligations to stand up to injustice.

“It’s Saudi foreign policy and the oppressive nature of Saudi society that’s stopping me,” the 28-year-old British academic told the Thomson Reuters Foundation.

“It’s not me saying I don’t want to go – I would love to be able to fulfil my religious obligation. But for as long as that would mean being complicit in violence, I won’t do it.”

A Saudi-backed coalition has waged war in Yemen since 2015 and aid workers say some 24 million people – almost 80% of the population – will likely need humanitarian assistance in 2019.

The Gulf kingdom also faces heightened scrutiny over its human rights record after last year’s murder of journalist Jamal Khashoggi by Saudi agents.

One of the most prominent Muslim leaders to endorse the boycott is Sadiq al-Gharawani, the Sunni Muslim grand mufti of Libya. Muslim organizations in several counties outside the Middle East, including the United States, have urged their members to consider the boycott, commonly citing the war in Yemen as the primary reason.

Saudi officials dismissed the boycott as an “unwise” attempt to “politicize the hajj” and noted the pilgrimage has been growing in recent years. The organizers insist younger Muslims are more likely to delay their pilgrimage to “stand against oppression” and hit the Saudi government where it hurts, because the hajj is not only a source of prestige for the Saudis but also a source of tourist income the monarchy cannot do without as it reduces its dependence on oil sales.

The pilgrims this year include survivors and relatives of the mosque attack in Christchurch, New Zealand, attending as guests of Saudi King Salman bin Abdulaziz.

“The most important thing is that the New Zealand community, including Muslims, they stood together against hate. And we are still saying that hate is not going to divide us. We will continue to love each other,” said Gamal Fouda, imam at one of the Christchurch mosques.

The hajj has previously been the subject of political controversy during times of heightened tension between Saudi Arabia and Iran, and when the Saudis were criticized for not providing enough amenities, security, and emergency services for the enormous crowd of visitors. Among other infrastructure improvements made to address these complaints, the Saudis announced that 2019 will be the first year when high-speed rail service is available from the airport to major locations along the pilgrimage route.