Osh, Kyrgyzstan (CNN) -- The first U.N. aid plane arrived Wednesday in Uzbekistan to help the thousands of people who have fled ethnic clashes in neighboring Kyrgyzstan, officials with a U.N. Refugee agency said Wednesday.
The cargo plane carrying about 800 lightweight tents will add to a growing effort to try and aid the estimated 100,000 people who have fled fighting in Kyrgyzstan for refugee camps in Uzbekistan. Several countries, including the United States, Germany and Russia, also have sent aid.
The International Committee of the Red Cross has said tens of thousands more people are displaced within Kyrgyzstan and the scope of the humanitarian crisis is "immense."
U.N. Secretary-General Ban Ki-moon called Uzbekistan's President Islam Karimov from London on Wednesday, thanking Karimov for his help with the humanitarian situation, according to a statement from Ban's office. The secretary-general promised assistance to affected people in southern Kyrgystan and those seeking refuge in Uzbekistan, and said he intended to consult with key members of the U.N. Security Council upon his return to New York later Wednesday.
Relative calm continued in Osh, Kyrgyzstan's second largest city, Wednesday. But still sporadic gunfire could be heard.
The Central Asian nation's news agency 24.kg reported that the death toll had risen to 179, a number that some observers discounted as low. Kyrgyzstan's interim government had declared Wednesday a day of mourning for families of the many killed and thousands wounded in the violence that started last week.
The government had sent extra security forces into Osh and Jalal-Abad, the hardest-hit cities, on Tuesday to help calm the situation. The ICRC says it was able to visit the main detention center in Osh Wednesday for the first time since the crisis started and has delivered food provided by the World Food Program to around 1,000 detainees.
The WFP says it has 3,000 metric tons (about 6.6 million pounds) of food -- mainly wheat flour and oil -- in ready for distribution in Kyrgyzstan. The WFP says that's enough to feed 87,000 people for two months -- and as long as its personnel can get safe and unimpeded access to those in need, they're prepared to bring the food.
However, the WFP says transporting aid from the Kyrgyz capital, Bishkek, is difficult, because the roads aren't safe and commercial trucking companies are reluctant to risk their vehicles.
The pressing issue for many aid groups Wednesday was trying to deal with refugee camps that were overwhelmed with refugees. The ICRC is particularly concerned with hygiene, "with many people drinking from irrigation ditches and reports of spreading dysentery," ICRC Anna Nelson said.
The clashes are part of the most serious outbreak of ethnic violence in the former Soviet republic since 1990, when hundreds of people died in skirmishes between Uzbeks and Kyrgyz in Osh.
"The past 20 years have been spent working very hard to avoid this kind of conflict, but everyone is aware of the danger, Rupert Colville, a spokesman for the UN refugee agency UNHCR, told CNN. "The situation is like a striking a match on petrol."
It was not clear what sparked the violence, which came weeks after bloody protests removed Kyrgyz President Kurmanbek Bakiev from office. Colville said there's a strong consensus in the Kyrgyz government that this wasn't a spontaneous interethnic clash, but one that was orchestrated and deliberately provocative.
"It's very hard to confirm anything for sure, but cross-checking seems to indicate a planned, provocative act. The Kyrgyz government is naming names, but UNHCR is not in a position to name names or point fingers," said Colville.
In recent days, more than 100,000 ethnic Uzbeks have fled the clashes with ethnic Kyrgyz, into camps in Uzbekistan, according to Uzbekistan's Foreign Ministry.
The flow of people was so overwhelming that Uzbekistan had close some of its border crossing areas leaving many standing at the border on the Kyrgyzstan side of a barbed-wire fence.
Many ethnic Uzbeks that have remained in Kyrgyzstan have had to hide out in abandoned buildings.
Red Cross workers came across one mosque outside Jalal-Abad where an estimated 6,000 frightened people have gathered for safety.
CNN's Matthew Chance, Brian Walker, Jill Dougherty, Nic Robertson and Evan Buxbaum contributed to this report.