A ban on international flights into Iraq's Kurdish region was being imposed on Friday after the Baghdad government retaliated against a vote for independence that has drawn opposition from foreign powers.
Iraq's Kurds overwhelmingly backed independence in a referendum on Monday, defying neighbouring countries which fear the vote could lead to renewed conflict in the region.
Almost all foreign airlines suspended flights to Erbil and Sulaimaniya, obeying a notice from the government in Baghdad, which controls Iraqi air space. The ban was set to come into force at 1500 GMT on Friday.
Domestic flights are still allowed, so travellers are expected to travel to Kurdistan mostly via Baghdad's airport, which will come under strain from the extra traffic.
Erbil airport was busier than usual on Friday as passengers scrambled to catch the last flights out.
Maintaining the travel curbs is likely to discourage visits by businessmen and Kurdish expatriates, and affect industries including hotels, financial services, transport and real estate. Over 400 Kurdish travel and tourism companies are directly affected by the flight ban and 7,000 are jobs at risk in the sector, Erbil-based Rudaw TV said.
The Kurdistan Regional Government meanwhile refused to hand over control of its border crossings to the Iraqi government, as demanded by Iraq, Iran and Turkey in retaliation for the independence referendum.
As the crisis unfolded, Iraq's top Shia cleric intervened to oppose the secession of the Kurdistan region, adding to pressure on the Kurds in his first directly political sermon since early last year.
Grand Ayatollah Ali al-Sistani asked the Kurdistan Regional Government (KRG) "to return to the constitutional path" in pursuing self-determination for the Kurdish people, a representative said in a sermon on his behalf.
"Any attempt to make secession an accomplished fact will lead to undesired consequences affecting Kurdish citizens," the sermon said.
Turkey, which has already threatened economic sanctions and a military response to any security challenges posed by the referendum result in neighbouring northern Iraq, has maintained a drumbeat of opposition to the Kurdish vote.
After talks in Ankara with Russian President Vladimir Putin on Thursday, Turkish President Tayyip Erdogan said the referendum was illegitimate and Russia and Turkey agreed that the territorial integrity of Iraq must be preserved.
Turkey and Russia have strong commercial ties with the semi-autonomous Kurdish region in Iraq. But the vote has alarmed Ankara as it battles a separatist insurgency from its own large Kurdish minority.