A series of blasts struck three churches across the provincial capital of Surabaya at around 7 a.m., leaving at least 13 dead and over 40 others wounded. The Islamic State group has claimed responsibility for the suicide attacks via its propaganda agency Amaq.

Australian Prime Minister Malcolm Turnbull and Foreign Minister Julie Bishop issued a joint statement late on Sunday, condemning what they called "cowardly" terrorist attacks on peaceful religious gatherings.

“Our two nations share a common commitment to mutual respect and diversity and we reject those who seek to spread division and hatred,” they said in a statement issued on Twitter.

Singapore’s top diplomat, Vivian Balakrishnan, also took to social media to express his deep sadness over the “appalling bomb attacks”.

“We strongly condemn this mindless act, which has taken several lives and injured others,” he said in a post on his Facebook page on Sunday.

Britain’s Minister of State for Asia and the Pacific, Mark Field, contributed a tweet of his own, expressing solidarity with the people of Indonesia. “Appalled by terrorist attack this morning in Surabaya. We stand with the people of Indonesia at this difficult time. #KamiTidakTakut,” he tweeted, using an Indonesian translation of the #WeAreNotAfraid hashtag.

A Korean Foreign Ministry spokesperson also issued comments on the terrorist attack, saying the South Korean government "strongly condemned" the incident, and expressed its intent to cooperate hand-in-hand with Indonesia to fight "the terrors that threaten all of humanity".

The European Union’s Ambassador to Indonesia, Vincent Guerend, “strongly condemned” the attack on places of worship irrespective of religion and said the EU “stands ready to continue our dialogue and cooperation”.

“We’re faced with same challenges in Europe, and we have to support each other,” Guerend told The Jakarta Post on Sunday.

He declined, however, to comment on whether the incident had any effect on European business interests in Indonesia, appealing instead to focus on the plight of the victims.

Later that day, Brussels issued its own statement extending condolences to the friends and families of those killed in the  blasts.

“Attacks on communities at prayer run counter to Indonesia’s traditional culture of religious diversity and inter-religious harmony. Such a culture is a source of inspiration for many around the world, especially in times, such as now, of tension,” EU spokesperson Maja Kocijancic said in the statement.

And while concerns about terrorism in Indonesia are on the rise, most statements issued by foreign embassies in response to the attacks did not warn against general travel to Indonesia.

On the EU’s website for consular protection for EU citizens abroad, most member states called on their citizens to remain cautious and warned against traveling to certain areas in Indonesia.

The Australian government’s Smartraveller website continues to advise its citizens in Indonesia to “exercise a high degree of caution in Indonesia, including in Bali, Surabaya and Jakarta, because of the high threat of terrorist attack”.

It also says there is a heightened risk of further terrorist attacks in the lead-up to and during Islam’s holy month of Ramadhan, which runs from mid-May to mid-June.

The United Kingdom government website also updated its foreign travel advice to reflect the latest incident, but without much change in its assessment of travel safety in Indonesia. "Around 360,000 British nationals visit Indonesia every year. Most visits are trouble free," it said. (tjs)