LAHORE, Pakistan — Thousands of Islamists in Pakistan launched a march toward the capital on Wednesday to protest a far-right Dutch lawmaker’s plans to hold a Prophet Muhammad cartoon contest later this year.

Pakistan’s newly elected government has denounced the contest, calling it an attempt to defame Islam. Physical depictions of God or the prophet, even positive ones, are forbidden in Islam and considered deeply offensive.

The protest was organized by Islamist groups that made surprising gains in Pakistan’s July elections. About 10,000 protesters took part in the march, chanting, “We will die to protect the honor of the prophet.”

The protesters refused demands from authorities to confine their rally to the eastern city of Lahore, where it began. They are expected to reach Islamabad on Thursday.

The cartoon contest is being organized by Geert Wilders, a far-right Dutch lawmaker with a history of incendiary remarks about Islam. The Dutch government has distanced itself from the event while saying it is committed to free speech.

Pakistan’s new prime minister, Imran Khan, has largely sided with the protesters, vowing to take the matter to the United Nations. His government has summoned the Dutch ambassador to lodge a formal protest, but has so far dismissed calls to expel the envoy.

Tehreek-i-Labaik, a hard-line Islamist group that helped organized the protests, supported Khan’s bid to be prime minister.

Tehreek-i-Labaik disrupted life in Islamabad with a three-week rally last year against an omitted reference to the prophet in a constitutional bill. Organizers say this time they will disperse after a daylong protest.

On Tuesday, Dutch news reports suggested that a man who was detained there on suspicion of threatening to attack Wilders and parliament was a Pakistani national. Police said they detained a 26-year-old suspect who is likely to be arraigned on Friday.

Wilders has for years lived under round-the-clock security due to repeated death threats linked to his criticism of Islam.

Emotions have been running high in Pakistan, where blasphemy is punishable by death and where the mere accusation of it can cause lynchings.

A former Pakistani cricketer, Khalid Latif, has offered a $28,000 reward for anyone who would “kill the Dutchmen” behind the blasphemous contest.

Pakistan’s Foreign Minister Shah Mahmood Qureshi has spoken with his Dutch counterpart about the “abominable and sacrilegious competition” this week.