Explosions shook the suburbs of the Yemeni port city of Aden on Monday as residents reported a foreign warship shelling Houthi positions on the outskirts of the city.
Street fighting and heavy shelling has for several days torn through the city, the last bastion of support for Saudi-backed president Abd-Rabbu Mansour Hadi.
Twelve days of bombing by a Saudi-led coalition has failed to halt the advance of the Iran-allied Houthis.
Relief from outside appeared distant as the International Committee of the Red Cross told Reuters that it had yet to arrange a flight to deliver 48 tons of medical supplies despite gaining Saudi approval for the aid on Saturday night.
Food, water and electricity shortages have mounted throughout the country but especially in Aden, where combat has shut ports and cut land routes linking the city to the outside.
The International Committee of the Red Cross, which for days blamed the Saudi-led coalition for delays, told Reuters on Monday that Saudi Arabia had granted permission for an aid shipment before midnight on Saturday but problems in chartering planes would likely delay the aid's arrival to the Yemeni capital for at least a day.
This comes as Saudi Arabia asked Pakistan for military aircraft, warships and soldiers, Pakistani Defense Minister Khawaja Asif said on Monday, at the start of a parliamentary debate on whether Pakistan should get involved in a Saudi-led campaign in Yemen.
Saudi Arabia, the Gulf's main Sunni Muslim power, has asked Sunni-majority Pakistan to join a Saudi-led military coalition that began conducting air strikes last month against largely Shi'ite Houthi forces in Yemen.
Sharif has in turn hedged his bets. He has said repeatedly he will defend any threat to Saudi Arabia's "territorial integrity" without defining what action such a threat might provoke.
"Saudi Arabia has asked for combat planes, warships and soldiers," Asif, who also visited Turkey to discuss Yemen, said, without specifying where Saudi wanted them deployed.
"Both Pakistan and Turkey are concerned at the overthrow of illegitimate government of Yemen by use of force by non-state actors ... Pakistan and Turkey agreed that the continuing crisis in Yemen could plunge the region into turmoil."
Arif Rafiq, a Washington-based adjunct scholar with the Middle East Institute, said earlier Pakistan was hoping to satisfy Saudi expectations at a "minimal" level.
"They're unlikely to be part of any meaningful action inside Yemen," he told Reuters. "Maybe they will reinforce the border."
Sharif owes the Saudis. Endemic tax dodging means Pakistan needs regular injections of foreign cash to avoid economic meltdown. Last year, the Saudis gave Pakistan $1.5 billion. Saudi Arabia also sheltered Sharif after he was overthrown in a 1999 military coup.
But joining the Saudi-led coalition could inflame a sectarian conflict at home where about a fifth of the population is Shi'ite and attacks on Shi'ites are increasing, further destabilizing the nuclear-armed nation of 180 million people.
Pakistani intervention would probably also anger Shi'ite power Iran, which shares a long and porous border in a region roiling with its own separatist insurgency. Pakistan's other main borders are with arch enemy India and Afghanistan, where Pakistani troops are conducting anti-militant operations. The Iranian foreign minister will visit Pakistan this week.
REUTERS