Demonstrations have taken place in Pakistan's port city of Karachi against the hanging of a militant leader by Iran.
Abdolmalek Rigi was head of the Jundullah militant group.
It says that it is fighting for the rights of minority Sunni Muslims in Iran's Sistan-Baluchistan province.
Iranian authorities say the group is involved in dozens of deadly attacks, including one which killed 40 members of the Revolutionary Guard in 2009.
Iran says the group, which operates out of Pakistan's Balochistan province, has the support of Pakistani, US and British intelligence agencies.
"Abdolmalek Rigi's only fault was that he spoke for the rights of the Baloch," Abdul Wahab Baloch, who led the demonstration, told the BBC.
Mr Baloch is a leader of the Baloch National Front, an alliance fighting for the rights of the impoverished province.
He was speaking as demonstrators holding posters of Mr Rigi stood by, chanting anti-Iranian slogans.
Mr Baloch said that Mr Rigi was a Baloch hero.
"Jundullah is a Baloch nationalist organisation - it has wrongly been labelled a sectarian group," he said.
"It is fighting for the rights of the Baloch in Iran, which is a largely Shia country.
"That is why we have been called a Sunni group."
Mr Baloch said that Iran had used large-scale repression to crush the Baloch.
"At least 700 Baloch have been hanged in Iran during the last two years," he said.
"They include religious leaders, politicians and intellectuals."
He said his party was in touch with Jundullah and they planned to launch a united front in both Pakistan and Iran.
"We are fighting both Iran and Pakistan for our rights and control of our land," he added.
Nationalist groups in Pakistan have been a thorn in the side of the government for several years.
However, this is the first time they had expressed solidarity with secessionist groups in Iran.