The Reuters news agency has spoken to hospital officials and police in Colombo after hotels and churches were targeted on Easter Sunday.
The first blast ripped through St Anthony's Shrine in Colombo.
Alex Agileson, who was in the vicinity, said buildings in the surrounding area shook with the blast.
A second explosion was reported at St Sebastian's Church in Negombo, a Catholic majority town north of Colombo.
A security official said the explosions hit three churches and three hotels frequented by foreign tourists.
Sri Lanka Bombings:
— PM Breaking News (@PMBreakingNews) 21 April 2019
- Massive explosions strike 3 churches and 3 hotels in coordinated Easter Sunday attack in Sri Lanka
- At least 160 dead, 368 injured
- 2 of the attacks were suicide bombings
- Sri Lankan police were warned of bombings last weekpic.twitter.com/lkFOWy1kyh
The official suspected at least two of the blasts were caused by suicide bombers.
National Hospital spokesman Dr Samindi Samarakoon says the nearly 300 wounded have been admitted to the capital Colombo's main hospital.
The UK foreign office says British nationals should follow travel advice from local authorities.
Foreign secretary Jeremy Hunt said he was shocked by the attacks.
He tweeted: "I'm deeply shocked and saddened by the horrifying attacks on churches and hotels in Sri Lanka today.
"To target those gathered for worship on Easter Sunday is particularly wicked.
"My prayers are with the victims and their families, and with those assisting in the response."
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