Assassinations of two international aid workers in Bangladesh over the last ten days have raised concern that global terrorists are taking advantage of political polarization in the country and linking up with local extremist groups to destabilize the South Asian democratic nation.

On Sept. 28, an Italian aid worker was gunned down while jogging in the streets of Dhaka. The Islamic State (ISIS) claimed responsibility for the attack, although the Bangladeshi government has denied that ISIS was involved. Five days later, masked gunmen riding on a motorbike killed a Japanese agricultural worker in northern Bangladesh.

The attacks follow the murders of four secular bloggers since the beginning of the year and have raised alarm among the expatriate community in Bangladesh.

Whether local groups are acting alone or have been motivated or directed by international terrorist groups like al-Qaeda in the Indian Subcontinent (AQIS) or ISIS remains a question.

One thing is certain: There is a serious terrorist threat brewing in the country, and the current political polarization between Bangladeshi Prime Minister Sheikh Hasina and opposition leader Khaleda Zia is feeding the problem.

The Hasina government claims that the violence is being perpetrated by the opposition Bangladesh National party (BNP) and Jamaat-e-Islami (JeI), whose leaders have been embroiled in war crimes trials that have already resulted in the executions of two JeI leaders.

In mid-September, Hasina called on the British government to take action against Bangladeshi diaspora communities in the U.K. that were stoking religious extremism in Bangladesh. She claimed that JeI leaders located in the U.K. were funding extremist activity in Bangladesh. Her claims followed the arrest of a British man of Bangladeshi origin, Touhidur Rahman, in Dhaka last month after he was alleged to be the mastermind behind at least two of the blogger murders.

Over the past year, the Bangladeshi authorities have arrested several members of the banned Jamaat-ul-Mujahideen Bangaldesh (JMB) extremist group, who were alleged to have either made or tried to make contact with ISIS. In May, Bangladesh arrested a regional coordinator of JMB who had allegedly sought to send operatives to Iraq and Syria from Bangladesh.

The possibility that the recent attacks on the international aid workers have global connections to groups like AQIS and ISIS makes it imperative that the Bangladesh government conduct a speedy and transparent investigation in cooperation with international authorities.

The U.S. must support the Hasina government in its efforts to get a handle on the rising extremist threat.

Washington also should take a more assertive role in encouraging political dialogue between Hasina and Zia. As I argued in congressional testimony in April, political deadlock between the ruling Awami League and BNP opposition is opening the door for Islamist extremists to gain more recruits and increase their influence in the country.

This past week’s assassinations signal they may already be pushing on that open door.