Two Kiwi sisters heard "huge explosions" near their hotel in Colombo - part of co-ordinated bomb blasts across Sri Lanka that have killed more than 200 people and left hundreds injured.

Colleen Dunning from Queenstown and Erin Clark from Auckland had been staying at Galle Face Hotel, along the waterfront from Shangri-La and Grand Cinnamon hotels where explosions occurred on Easter Sunday.

"We were walking along the waterfront this morning, where families were gathering for a day on the green. We heard a huge explosion followed by sirens and then a few minutes later there was another explosion which was very close to our hotel," Dunning said.

They turned back to their hotel, unaware of the scale of the devastation that had happened, and were only informed about 30 minutes later by their tour guide as they made their way out of the city.

They were now down the coast in the city of Galle, and while they were under curfew felt "very safe and have no concerns for our safety".

"We feel for the beautiful people of Sri Lanka," Dunning said.

Other attacks occurred in Negombo, north of Colombo, and in Batticaloa, on the country's east coast.

Another Auckland woman, Rachel Stephens, said local military had set up barricades in Colombo, hospitals were overflowing and people were everywhere following the Easter Sunday attacks.

Stephens said she had attended some of the sites the explosions went off "less than 24 hours ago" and next to the hotel she pulled up to stay at.

The 25-year-old said she had only been in Sri Lanka for two days before the attacks took place and is still finding her bearings.

The Ministry of Foreign Affairs told the Herald 214 New Zealanders were registered as being in the South Asian country.

However, there were no reports of any New Zealand citizens being caught up in the explosions.

"New Zealanders in Sri Lanka are advised to exercise a high degree of vigilance in public areas and to follow any advice issued by local authorities," an Mfat spokesperson said.

"New Zealanders in Sri Lanka in need of consular assistance should contact the New Zealand High Commission in New Delhi on +91 11 468 83170."

Kiwis in the country are being asked to register their details at www.safetravel.govt.nz.

Meanwhile, another New Zealand woman, Jane Burdon, said she was on the streets of Colombo when the first explosion went off.

She did not hear the blast but as soon as their driver heard news of the bombings, it was straight back to the hotel.

"Everyone here in the hotel is shocked as since the war ended they have felt safe," Burdon told the Herald.

"We are extremely safe and being well looked after in our very small hotel in the suburbs of Colombo.

"We have been travelling this beautiful country for the last three weeks. We have been totally spoilt by Sri Lankans' hospitality."

Burdon said she was flying back to New Zealand on Wednesday morning and they would stay at the hotel until then.

However, their plans could change and they could head to the airport tomorrow night before the curfew.

"We are concerned about being here until Wednesday morning but we have no choice so have to be patient," she said.

Sri Lanka security officials said six near-simultaneous blasts hit three churches and three hotels frequented by tourists.

The New York Times has reported at least 207 people have died in the attacks.

A Sri Lanka state-run newspaper, the Daily News, reported that more than 500 people have been hospitalised with injuries caused by the blasts.

An official said they suspect the blasts at two churches were carried out by suicide bombers.

"Eighty people have already been admitted, and more are still coming in," an official at the Colombo National Hospital told AFP earlier on condition of anonymity.

The nature of the explosions was not immediately clear.