Thousands of protesters took to the streets of Pakistan's major cities Friday to condemn a crackdown on Rohingya Muslims in Myanmar, with many carrying placards stating "Shame on Aung San Suu Kyi".

The largely peaceful rallies were spearheaded by Islamist party Jamaat-e-Islami (JI), but other groups including mainstream political parties joined in.

Leaders including JI chief Sirajul Haq called for an end to the "genocide" of the Rohingya and for Pakistan to break off relations with the government in Myanmar.

Pakistan has previously expressed "deep anguish" at the violence.

Many protesters also slammed Suu Kyi, Myanmar's de facto leader, over her silence. The Nobel Peace Prize winner has faced criticism for failing to condemn the violence, leaving her global reputation in tatters.

A senior United Nations representative told AFP Friday that more than 1,000 people may already have been killed in the military-led crackdown, which has seen 270,000 mostly Rohingya civilians flee to Bangladesh in the last two weeks alone.

Others have died trying to flee the fighting in Rakhine state, where witnesses say entire villages have been burned since Rohingya militants launched a series of coordinated attacks on August 25, prompting the crackdown.

In Karachi, which hosts one of the largest Rohingya populations outside of Myanmar, more than 2,000 people demonstrated outside the Karachi Press Club.

"If our leader gives the call, we will lay down our lives for the Burmese Muslims," one protester, Maulana Ahmed, told AFP.

In Islamabad, a similarly sized crowd gathered at the entrance to the diplomatic enclave, inside which the Myanmar embassy is situated.

Many carried placards reading: "Why are these Muslims being killed? What is their crime?" as chants of "Allahu Akbar", or "God is the Greatest", reverberated.

There were also some sporadic calls for "jihad", or holy war.

Security forces with protective riot gear stood nearby and containers blocked off access to the enclave, with some small scuffles.

But police appeared relaxed as the demonstrators, some armed with batons, showed no signs of trying to go further into the diplomatic area.

Protests were also held in deeply religious neighbouring Afghanistan Friday.

Hundreds of placard-waving men marched in the eastern city of Jalalabad in support of the Rohingya while smaller demonstrations were held in the capital Kabul, including one outside the compound of the United Nations Assistance Mission in Afghanistan, and other cities.

Earlier in the week the Afghan foreign ministry condemned the "barbaric and inhumane attacks". The Taliban insurgents have also spoken out in support, urging followers to help the "oppressed Muslims".

Malaysia and Bangladesh also saw protests Friday evening.

The Rohingya have long been subjected to discrimination in mostly Buddhist Myanmar, which regards them as illegal immigrants from Bangladesh and denies them citizenship.

The death toll given to AFP by Yanghee Lee, the UN special rapporteur on human rights in Myanmar, is far higher than official tolls totalling 432.