The US has issued a travel warning to its citizens visiting Pakistan, Afghanistan and Bangladesh and said extremist elements are also "active" in India.
The warning came on a day President Donald Trump's administration issued a new executive order temporarily barring citizens of six Muslim-majority nations from entering the United States but exempted those with valid visas.
"The US government assesses terrorist groups in South Asia may be planning attacks in the region, possibly against US facilities, citizens, and interests. US citizens should avoid travel to Afghanistan, as no region in the country is immune from violence," the US State Department said in its worldwide caution on Monday.
"A number of established terrorist organisations, indigenous sectarian groups, and other militants pose a danger to US citizens in Pakistan."
"Extremist elements are also active in India, as outlined in a recent emergency message. Terrorists have hit a wide variety of targets and institutions in Bangladesh," the advisory stated.
On Monday, Trump signed a revised version of his executive order on immigration, that places a 90-day ban on people from six predominantly Muslim nations.
The new order, which excludes Iraq from the original list of seven countries, will go into effect from March 16. The executive order bars citizens from Sudan, Syria, Iran, Libya, Somalia and Yemen from entering America for 90 days.
President Trump signed the new order behind closed doors around 11.30am, NBC reported.
Iraq was removed from the list after assurances from the Iraqi government of increased information sharing with the US, a senior Department of Homeland Security official told reporters on Monday.
Visas revoked because of the original travel ban have been fully restored, according to the State Department.
"To our allies and partners around the word, please understand this order is part of our ongoing efforts to eliminate vulnerabilities that radical Islamic terrorists can and will exploit for destructive ends," Secretary of State Rex Tillerson said after the executive order's signing.
Tillerson, Homeland Security Secretary John Kelly and Attorney General Jeff Sessions unveiled the order in front of reporters.
The directive includes a 120-day ban on all refugees.
A three-judge panel from the Ninth US Circuit Court of Appeals had in early February ruled unanimously to uphold a federal judge's restraining order on the travel ban, delaying the executive order's implementation.
Kelly said the US needed a "rigorous review" of visa and refugee programmes. "We cannot risk the prospect of malevolent actors using our immigration system to take American lives," he said.
The earlier order had sparked chaos at airports around the world as airlines refused to let passengers with visas on to flights bound for the US.